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    Length: 55872 (0xda40)
    Types: TextFile
    Names: »Dembart.virus.article.ps«

└─⟦4f9d7c866⟧ Bits:30007245 EUUGD6: Sikkerheds distributionen
    └─⟦this⟧ »./papers/Virus/Dembart.virus.article.ps« 

TextFile

%!
% This file is a NONconforming PostScript file.
(TeXPS: dvi->PostScript Driver dvi2ps, Version 3.11 of September 5, 1990\n)print flush
(TeXPS: release number dvi2ps of 3.11\n)print flush
% Copyright 1989 Stephan v. Bechtolsheim (unless otherwise stated)
% applies to various prologue files. Read documentation for details.
save
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/texpre.pro"
/@bop0
{
PsPrintEnabled { (Pass0: Page ) print == flush } {pop} ifelse
}	def
/@eop0 {
pop
}	def
/@bop1
{
PsPrintEnabled { (Pass1: Page ) print == flush } {pop} ifelse
save
DviTranslateVector-X DviTranslateVector-Y translate
DviOrientationMatrix concat
Page-H-Offset Page-V-Offset translate
3 1 roll
translate
0 0 moveto
Draft-Flag { @Draft } if
/DriverDelta 0 def
} def
/@eop1 {
pop
showpage
restore
} def
/@end {
(Done!\n) print flush
} def
/@ReportVmStatus {
(\n@ReportVmStatus: ) print
print (: ) print
vmstatus
(max: ) print 20 string cvs print
(, used: ) print 20 string cvs print
(, level: ) print 20 string cvs print
(\n) print flush
} def
/@ReportVmStatusNew {
(VM: ) print
exch print
(, printer: ) print
/Vmfree vmstatus pop exch pop def Vmfree (       ) cvs print
(, driver: ) print dup (      ) cvs print
(, delta: ) print
Vmfree sub (      ) cvs print
(\n) print flush
} def
/@Draft {
gsave
Page-H-Offset neg Page-V-Offset neg translate
-45 rotate
-150 0 moveto
/Helvetica-Bold findfont
[120.0 0 0 -120.0 0 0 ] makefont setfont
(DRAFT)  true charpath stroke
grestore
gsave
Page-H-Offset neg Page-V-Offset neg translate
300 -100 moveto
/Helvetica-Bold findfont
[60.0 0 0   -60.0 0 0 ] makefont setfont
Date-and-Time		show
(   ::   )	      	show
Dvi-File-Name		show
grestore
} def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/texpre.pro"
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/pos.pro"
/a { rmoveto } def
/DriverDelta 0 def
/b { exch p dup /DriverDelta exch def 0 rmoveto } def
/c { p DriverDelta 4 sub dup /DriverDelta exch def 0 rmoveto } def
/d { p DriverDelta 3 sub dup /DriverDelta exch def 0 rmoveto } def
/e { p DriverDelta 2 sub dup /DriverDelta exch def 0 rmoveto } def
/f { p DriverDelta 1 sub dup /DriverDelta exch def 0 rmoveto } def
/g { p DriverDelta 0 rmoveto } def
/h { p DriverDelta 1 add dup /DriverDelta exch def 0 rmoveto } def
/i { p DriverDelta 2 add dup /DriverDelta exch def 0 rmoveto } def
/j { p DriverDelta 3 add dup /DriverDelta exch def 0 rmoveto } def
/k { p DriverDelta 4 add dup /DriverDelta exch def 0 rmoveto } def
/l { p -4 0 rmoveto } def
/m { p -3 0 rmoveto } def
/n { p -2 0 rmoveto } def
/o { p -1 0 rmoveto } def
/q { p 1 0 rmoveto } def
/r { p 2 0 rmoveto } def
/s { p 3 0 rmoveto } def
/t { p 4 0 rmoveto } def
/p { show } def
/w { 0 exch rmoveto } def
/x { 0 rmoveto } def
/y { 3 -1 roll p rmoveto } def
/u-string ( ) def
/u { u-string exch 0 exch put
u-string show
} def
/v { u-string exch 0 exch put
currentpoint
u-string show
moveto
} def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/pos.pro"
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/rules.pro"
/z
{   /dy exch def
/dx exch def
currentpoint
currentpoint
transform round exch round exch itransform
newpath
moveto
dx 0 rlineto
0 dy rlineto
dx neg 0 rlineto
closepath
fill
moveto
}
def
/z
{   /dy exch def
/dx exch def
currentpoint
0.2 0.2 rmoveto
currentpoint
newpath
moveto
dx 0 rlineto
0 dy rlineto
dx neg 0 rlineto
closepath
fill
moveto
}
def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/rules.pro"
letter
/Dvi-File-Name (virus.article.dvi) def
(Dvi file name: ") print Dvi-File-Name print (".\n) print
/Draft-Flag false def
/#copies 1 def
/NumCharsInPixelFonts 256 def
/HostName (nisc.jvnc.net) def
(This PostScript file was produced on host \") print HostName print (\".\n) print
/PsPrintEnabled true def
/Page-H-Offset   0.000000 def
/Page-V-Offset   0.000000 def
/ExecPsConv {0.30 mul} def
/Date-and-Time (Thu Jun 20 16:54 1991) def
/DviTranslateVector-X   72.000 def
/DviTranslateVector-Y  720.000 def
/DviOrientationMatrix [    0.240    0.000    0.000
	   -0.240 0.0 0.0 ] def
% dvi2ps: BEGIN including file "/usr/local/tex/lib/TeXPS/pro/pixel-fonts.pro"
/@newfont
{
/newname exch def
newname 7 dict def
newname load begin
/FontType 3 def
/FontMatrix [1 0 0 -1 0 0] def
/FontBBox [0 0 1 1] def
/BitMaps NumCharsInPixelFonts array def
/BuildChar {CharBuilder} def
/Encoding NumCharsInPixelFonts array def
0 1 NumCharsInPixelFonts 1 sub {Encoding exch /.undef put} for
end
newname newname load definefont pop
} def
/ch-image {ch-data 0 get} def
/ch-width {ch-data 1 get} def
/ch-height {ch-data 2 get} def
/ch-xoff  {ch-data 3 get} def
/ch-yoff  {ch-data 4 get} def
/ch-tfmw  {ch-data 5 get} def
/CharBuilder
{
/ch-code exch def
/font-dict exch def
/ch-data font-dict /BitMaps get ch-code get def
ch-data null eq not
{
ch-tfmw   0
ch-xoff neg
ch-height ch-yoff sub neg
ch-width  ch-xoff neg add
ch-yoff
setcachedevice
0 0 transform round exch round exch itransform translate
ch-width ch-height true
[1 0  0 1 ch-xoff ch-height ch-yoff sub] {ch-image} imagemask
}
if
} def
/@dc
{
/ch-code exch def
/ch-data exch def
currentfont /BitMaps get
ch-code ch-data put
currentfont /Encoding get
ch-code (   ) cvs   % convert the character code to a string
cvn
ch-code exch put
} def
/@sf /setfont load def
% dvi2ps: END including file "/usr/local/tex/lib/TeXPS/pro/pixel-fonts.pro"

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	 18 25 -1 24 22] 80 @dc
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	 19 18 -2 17 22] 97 @dc
[<
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	 21 18 0 17 22] 117 @dc
[<
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	 17 25 -2 24 22] 108 @dc
[<
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	 20 25 -1 24 22] 82 @dc
[<
70F8F8F870>
	 5 5 -8 4 22] 46 @dc
[<
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	 18 25 -2 24 22] 71 @dc
[<
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	 20 27 0 17 22] 112 @dc
[<
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	 17 21 -2 22 22] 60 @dc
[<
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	 21 25 0 24 22] 85 @dc
[<
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	 18 25 -2 24 22] 64 @dc
[<
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	 19 25 -1 24 22] 65 @dc
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	 15 25 -3 24 22] 73 @dc
[<
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	 19 25 -1 24 22] 77 @dc
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	 19 25 -1 24 22] 84 @dc
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	 19 25 -1 24 22] 69 @dc
[<
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	 19 25 0 24 22] 68 @dc
[<
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	 17 21 -2 22 22] 62 @dc
[<
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	 17 25 -2 24 22] 83 @dc
[<
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	 20 25 0 24 22] 98 @dc
[<
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	 13 35 -2 25 22] 106 @dc
[<
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	 16 18 -3 17 22] 101 @dc
[<
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	 16 18 -3 17 22] 99 @dc
[<
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	 17 23 -1 22 22] 116 @dc
[<
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	 19 18 -1 17 22] 118 @dc
[<
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	 16 26 -3 25 22] 105 @dc
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	 15 18 -3 17 22] 115 @dc
[<
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	 19 27 -1 17 22] 121 @dc
[<
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	 19 18 -1 17 22] 120 @dc
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	 17 25 -1 24 22] 102 @dc
[<
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	 20 25 -1 24 22] 100 @dc
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	 21 25 0 24 22] 104 @dc
[<
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	 21 18 0 17 22] 110 @dc
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	 19 18 -1 17 22] 119 @dc
[<
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	 7 11 -7 4 22] 44 @dc
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@F3 @sf
[<
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	 15 30 -4 29 23] 49 @dc

1 @eop0

0 0 1 @bop1 617 381 a @F1 @sf(Securit)n(y)22 b(Article)h(Extracts)-607 92 y 
@F0 @sf(Computer)g(Viruses)-390 171 y @F2 @sf(Lee)16 b(Dem)o(bart)-230 194 y 
@F5 @sf(Abstract)-892 158 y @F4 @sf(From:)21 b("Paul)f(R.)i(Grupp")e
(<GRUPP@AI.AI)o(.MIT.)o(EDU>)o -1000 50 a(Subject:)o 43 x(computer)o 21 x
(viruses)-525 100 y(Security)42 b(experts)g(are)21 b(afraid)g(that)g
(saboteurs)f(could)h(infect)42 b(computers)-1527 50 y(with)21 b(a)g
("virus")g(that)f(would)h(remain)g(latent)f(for)i(months)e(or)h(even)g
(years,)43 b(and)-1526 49 y(then)21 b(cause)f(chaos.)479 1583 y @F3 @sf(1)
-987 b
1 @eop1

2 @bop0
@F3 @sf
[<
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	 30 33 -3 31 36] 71 @dc
[<
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	 17 20 -1 19 20] 101 @dc
[<
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	 15 20 -1 19 18] 114 @dc
[<
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	 35 20 -1 19 38] 109 @dc
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	 30 20 -1 19 33] 119 @dc
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	 20 20 -2 19 23] 97 @dc
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	 16 32 0 31 14] 102 @dc
[<
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	 6 14 -4 4 13] 44 @dc
[<
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	 13 28 -1 27 18] 116 @dc
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	 22 32 -1 31 25] 104 @dc
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	 21 32 -2 31 25] 100 @dc
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	 11 32 0 31 13] 108 @dc
[<
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	 10 31 0 30 13] 105 @dc
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	 21 32 -1 31 25] 98 @dc
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	 13 20 -2 19 18] 115 @dc
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	 20 20 -1 19 23] 111 @dc
[<
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	 21 29 -1 19 24] 121 @dc
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	 16 20 -2 19 20] 99 @dc
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	 21 20 -1 19 24] 118 @dc
[<
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	 22 20 -1 19 25] 117 @dc
[<
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	 21 29 -1 19 25] 112 @dc
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	 22 20 -1 19 25] 110 @dc
[<
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	 20 31 -1 20 23] 103 @dc
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	 5 5 -4 4 13] 46 @dc
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	 32 31 -1 30 34] 89 @dc
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	 21 32 -1 31 24] 107 @dc
[<
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	 14 31 -1 30 16] 73 @dc
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	 16 20 -1 19 20] 122 @dc
[<
FFC0FFC0>
	 10 2 -1 10 15] 45 @dc
[<
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	 23 32 0 31 25] 12 @dc
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	 23 20 0 19 24] 120 @dc
[<
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	 28 31 -2 30 33] 84 @dc
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	 29 32 -2 30 34] 85 @dc
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	 18 33 -3 31 25] 83 @dc
[<
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	 26 33 -3 31 33] 67 @dc
[<
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	 30 32 -2 30 33] 82 @dc
[<
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	 25 31 -2 30 30] 70 @dc
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	 18 30 -2 29 23] 50 @dc
[<
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	 18 31 -2 29 23] 56 @dc
[<
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	 15 14 -5 31 23] 92 @dc
[<
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	 31 32 -1 30 34] 86 @dc
[<
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	 15 14 -2 31 23] 34 @dc
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	 29 31 -2 30 34] 78 @dc
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	 26 31 -2 30 32] 66 @dc
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	 29 31 -2 30 35] 68 @dc
[<
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	 7 45 -4 33 13] 91 @dc
[<
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	 7 45 -1 33 13] 93 @dc
[<
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	 29 32 0 31 27] 11 @dc
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	 21 29 -2 19 24] 113 @dc
[<
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	 5 29 -4 19 13] 59 @dc
[<
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	 6 14 -4 31 13] 39 @dc
[<
FFC03FFE1F0007E00E0003C0040003C002000780020007800200078001000F0001000F0001
000F0000FFFE0000801E0000801E0000403C0000403C0000403C0000207800002078000020
78000010F0000010F0000010F0000009E0000009E0000009E0000007C0000007C0000007C0
0000038000000380000003800000010000>
	 31 32 -1 31 34] 65 @dc
[<
3F006180F0C0F0606070007000700070007000700070007000700070007000700070007000
70007000700070007000700070007000F007F0007000000000000000000000000000E001F0
01F001F000E0>
	 12 40 2 30 14] 106 @dc
[<
70F8F8F8700000000000000000000070F8F8F870>
	 5 20 -4 19 13] 58 @dc

2 @eop0

0 0 2 @bop1 195 w @F3 @sf(Germ)16 b(w)o(arfare,)f(the)h(delib)q(erate)h
(release)f(of)g(deadly)g(bacteria)g(or)g(viruses,)g(is)g(a)g(practice)g
(so)g(abhorren)o(t)g(that)-1951 57 y(it)k(has)h(long)f(b)q(een)j(outla)o
(w)n(ed)d(b)o(y)h(in)o(ternational)e(treat)o(y)l(.)36 b(Y)l(et)22 b
(computer)f(scien)o(tists)e(are)i(confron)o(ting)f(the)-1950 56 y(p)q
(ossibilit)o(y)d(that)g(something)h(akin)g(to)f(germ)h(w)o(arfare)f(could)h
(b)q(e)h(used)g(to)f(disable)g(their)g(largest)f(mac)o(hines.)-1951 56 y
(In)h(a)f(civilizati)o(on)f(ev)o(er)h(more)g(dep)q(ende)q(n)o(t)h(on)f
(computers,)h(the)f(results)g(could)g(b)q(e)h(disastrous)e(-)h(the)h
(sudden)-1949 57 y(sh)o(utdo)o(wn)11 b(of)f(air)g(tra\016c)g(con)o(trol)g
(systems,)h(\014nancial)f(net)o(w)o(orks,)g(or)h(factories,)f(for)g
(example,)h(or)g(the)g(wholesale)-1951 56 y(destruction)k(of)g(go)o(v)o
(ernmen)o(t)f(or)g(business)i(records.)-923 102 y(The)f(w)o(arning)f(has)h
(b)q(een)h(raised)e(b)o(y)h(a)g(Univ)o(ersit)o(y)e(of)i(Southern)g
(California)e(researc)o(her)i(who)f(\014rst)h(describ)q(ed)-1949 56 y(the)
20 b(problem)f(in)h(Septem)o(b)q(er,)h(b)q(efore)f(t)o(w)o(o)f
(conferences)h(on)g(computer)g(securit)o(y)l(.)33 b(Researc)o(h)20 b(b)o
(y)g(graduate)-1951 57 y(studen)o(t)13 b(F)l(red)h(Cohen,)f(28,)g(sho)o
(ws)g(that)g(it)f(is)h(p)q(ossible)g(to)g(write)g(a)g(t)o(yp)q(e)g(of)g
(computer)g(program,)g(whimsicall)o(y)-1951 56 y(called)h(a)g(virus,)g
(that)g(can)h(in\014ltrate)e(and)i(attac)o(k)e(a)h(computer)h(system)f(in)g
(m)o(uc)o(h)h(the)f(same)h(w)o(a)o(y)e(a)h(real)g(virus)-1950 57 y
(infects)i(a)h(h)o(uman)g(b)q(eing.)24 b(Slipp)q(ed)18 b(in)o(to)d(a)i
(computer)g(b)o(y)f(some)h(clev)o(er)f(sab)q(oteur,)h(the)f(virus)h(w)o
(ould)f(spread)-1950 56 y(throughout)f(the)h(system)f(while)g(remaining)g
(hidden)i(from)d(its)h(op)q(erators.)21 b(Then,)16 b(at)f(some)g(time)g
(mon)o(ths)g(or)-1950 57 y(y)o(ears)e(later,)g(the)h(virus)g(w)o(ould)f
(emerge)h(without)f(w)o(arning)g(to)h(cripple)f(or)h(sh)o(ut)g(do)o(wn)g
(an)o(y)f(infected)h(mac)o(hine.)-1950 101 y(The)g(p)q(ossibilit)o(y)f
(has)h(computer)g(securit)o(y)g(exp)q(erts)g(alarmed)g(b)q(ecause,)h(as)f
(Cohen)g(w)o(arns,)f(the)i(programmi)o(ng)-1951 56 y(necessary)e(to)g
(create)g(the)h(simplest)e(forms)g(of)h(computer)h(virus)e(is)h(not)g
(particularly)f(di\016cult.)18 b(\\Viral)12 b(attac)o(ks)-1951 57 y(app)q
(ear)k(to)f(b)q(e)h(easy)f(to)g(dev)o(elop)h(in)f(a)g(short)g(time,")g(he)g
(told)g(a)g(conference)i(co-)f(sp)q(onsored)f(b)o(y)h(the)g(National)o -1951 
56 a(Bureau)g(of)f(Standards)h(and)g(the)g(Departmen)o(t)f(of)g(Defense.)
22 b(\\[They])15 b(can)h(b)q(e)g(designed)g(to)f(lea)o(v)o(e)g(few)h(if)f
(an)o(y)-1950 57 y(traces)20 b(in)g(most)g(curren)o(t)g(systems,)h(are)g
(e\013ectiv)o(e)e(against)h(mo)q(dern)g(securit)o(y)g(p)q(olicies,)h(and)g
(require)f(only)-1950 56 y(minimal)14 b(exp)q(ertise)h(to)g(implemen)o
(t.")-670 102 y(Computer)k(viruses)g(are)f(aptly)h(named;)i(they)e(share)g
(sev)o(eral)f(insidious)g(features)h(with)g(biologi)o(cal)f(viruses.)-1951 
56 y(Real)e(viruses)f(burro)o(w)h(in)o(to)e(living)h(cells)h(and)g(tak)o
(e)f(o)o(v)o(er)g(their)g(hosts')g(mac)o(hinery)h(to)f(mak)o(e)g(m)o
(ultiple)g(copies)-1950 57 y(of)j(themselv)o(es.)30 b(These)19 b(copies)f
(escap)q(e)h(to)f(infect)h(other)f(cells.)30 b(Usually)17 b(infected)i
(cells)f(die.)30 b(A)19 b(computer)-1950 56 y(virus)c(is)g(a)g(tin)o(y)g
(computer)h(program)e(that)h(\\infects")g(other)g(programs)f(in)i(m)o(uc)o
(h)f(the)h(same)f(w)o(a)o(y)l(.)21 b(The)15 b(virus)-1950 57 y(only)f(o)q
(ccupies)h(a)f(few)g(h)o(undred)h(b)o(ytes)f(of)g(memory;)f(a)h(t)o
(ypical)f(mainframe)g(program,)g(b)o(y)h(con)o(trast,)f(tak)o(es)g(up)-1949 
56 y(h)o(undreds)19 b(of)f(thousands.)29 b(Th)o(us,)18 b(when)h(the)g
(virus)e(is)h(inserted)g(in)o(to)f(an)i(ordinary)e(program,)g(its)h
(presence)-1949 56 y(go)q(es)d(unnoticed)h(b)o(y)f(computer)g(op)q
(erators)f(or)h(tec)o(hnicians.)-1064 102 y(Then,)k(eac)o(h)f(time)f(the)h
(\\host")f(program)g(runs,)i(the)f(computer)g(automatical)o(ly)e(executes)j
(the)f(instructions)-1951 56 y(of)i(the)h(virus-just)f(as)h(if)f(they)h(w)o
(ere)f(part)h(of)f(the)h(main)f(program.)36 b(A)20 b(t)o(ypical)g(virus)g
(migh)o(t)g(con)o(tain)g(the)-1950 57 y(follo)o(wi)o(ng)d(instructions:)
26 b(\\First,)18 b(susp)q(end)i(execution)e(of)h(the)f(host)g(program)g
(temp)q(orarily)l(.)29 b(Next,)19 b(searc)o(h)-1950 56 y(the)c(computer's)g
(memory)g(for)g(other)g(lik)o(ely)f(host)h(programs)f(that)h(ha)o(v)o(e)f
(not)h(b)q(een)i(already)e(infected.)20 b(If)c(one)-1950 57 y(is)g(found,)g
(insert)f(a)h(cop)o(y)g(of)f(these)h(instructions)f(in)o(to)g(it.)22 b
(Finally)l(,)14 b(return)i(con)o(trol)f(of)g(the)i(computer)e(to)h(the)-1950 
56 y(host)f(program.")-303 102 y(The)i(en)o(tire)g(sequence)h(of)f(steps)g
(tak)o(es)f(a)h(half)g(a)g(second)g(or)g(less)g(to)f(complete,)h(fast)f
(enough)i(so)f(that)f(no)h(on)-1950 56 y(will)f(b)q(e)i(a)o(w)o(are)d
(that)i(it)f(has)h(run.)26 b(And)18 b(eac)o(h)f(newly)g(infected)g(host)g
(program)f(helps)h(spread)g(the)g(con)o(tagion)-1951 57 y(eac)o(h)e(time)g
(it)f(runs,)h(so)g(that)g(ev)o(en)o(tually)f(ev)o(ery)h(program)f(in)h
(the)g(mac)o(hine)g(is)g(con)o(taminated.)-1677 101 y(The)d(virus)g(con)o
(tin)o(ues)g(to)g(spread)g(inde\014nitely)l(,)g(ev)o(en)h(infecting)f
(other)f(computers)h(whenev)o(er)h(a)f(con)o(taminated)-1951 56 y(program)h
(is)h(transmitted)f(to)h(them.)19 b(Then,)c(on)f(a)g(particular)f(date)i
(or)e(when)i(certain)f(pre-set)h(conditions)e(are)-1950 57 y(met,)18 b
(the)g(virus)f(and)h(all)f(it's)f(clones)i(go)f(on)h(the)g(attac)o(k.)26 b
(After)18 b(that,)f(eac)o(h)h(time)f(an)h(infected)g(program)e(is)-1950 
56 y(run,)e(the)f(virus)g(disrupts)g(the)h(computer's)f(op)q(erations)g(b)o
(y)g(deleting)g(\014les,)h(scram)o(bling)e(the)h(memory)l(,)g(turning)-1950 
57 y(o\013)h(the)i(p)q(o)o(w)o(er,)e(or)h(making)f(other)h(misc)o(hief.)
168 161 y(2)-987 b
2 @eop1

3 @bop0
@F3 @sf
[<
FFF8FFF80F800F8007800F0007800F0007800F0007800F0007800F0007800F0007800F0007
800F0007800F0007800F0007800F0007800F0007800F0007800F0007FFFF0007800F000780
0F0007800F0007800F0007800F0007800F0007800F0007800F0007800F0007800F0007800F
0007800F000F800F80FFF8FFF8>
	 29 31 -2 30 34] 72 @dc
[<
FFFFFF800F800F8007800180078000C0078000C00780004007800040078000400780002007
80002007800020078080000780800007808000078080000781800007FF8000078180000780
80000780800007808000078080800780008007800080078000800780018007800100078003
00078003000F800F00FFFFFF00>
	 27 31 -2 30 31] 69 @dc
[<
0FC000107000201800700C00780E0078060030070000070000038000038000038003E3C00E
13C0180BC03807C07007C07007C0F003C0F003C0F003C0F003C0F003C0F00380F003807003
807007003807003806001C0C000E180003F000>
	 18 31 -2 29 23] 57 @dc
[<
03000007800007800007800007800007800007800007800003800003800003800003800001
800001C00000C00000C0000040000040000020000020000010000008000008008004008002
008002004001007FFF807FFF807FFFC0400000>
	 18 31 -3 29 23] 55 @dc
[<
03E0000C3800100E00200600400700400380E00380F003C0F003C07003C00003C00003C000
03C0000380000380100780100700180E00161C0011F0001000001000001000001000001000
001000001FE0001FF8001FFC001FFE00180300>
	 18 31 -2 29 23] 53 @dc
[<
0F800030E000407000407800F03800F83C00F83C00F83C00203C00003C00003C00003C0000
3C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C00003C
00003C00003C00003C00003C00003C00007C000FFFC0>
	 18 32 -2 30 23] 74 @dc
[<
387CFCFCB8808080404020201008>
	 6 14 -3 31 13] 96 @dc
[<
03F0000E1C001C0E00180600380700780780700380700380700380F003C0F003C0F003C0F0
03C0F003C0F003C0F003C0F003C0F003C0F003C0F003C0F003C0F003C07003807003807003
807003803807001806001C0E000E1C0003F000>
	 18 31 -2 29 23] 48 @dc
[<
FFE01FFE1F8007E0070003C0020007C00100078001800F0000801F0000401E0000603C0000
207C00001078000018F8000009F0000005E0000007E0000003C00000078000000F8000000F
8000001E4000003E4000003C2000007C10000078100000F0080001F00C0001E0040003C002
0007C007000FE00FC07FF83FF8>
	 31 31 -1 30 34] 88 @dc
[<
FFFC00000FC000000780000007800000078000000780000007800000078000000780000007
800000078000000780000007800000078000000780000007FFE0000780780007801C000780
1E0007800F0007800F8007800F8007800F8007800F8007800F8007800F8007800F0007801E
0007801C000F807800FFFFE000>
	 25 31 -2 30 31] 80 @dc
[<
FFE0C1FFF81F00C01F800E00C00F000401E00F000401E00F000401E00F000403900F000403
900F000407080F000407080F000407080F00040E040F00040E040F00040E040F00041C020F
00041C020F00041C020F000438010F000438010F000438010F000470008F000470008F0004
70008F0004E0004F0004E0004F0005C0002F0005C0002F0005C0002F000780001F000F8000
1F80FF80001FF8>
	 37 31 -2 30 42] 77 @dc
[<
000400020000000C00030000000E00070000000E00070000001E00078000001F000F800000
1F000F8000001F000F8000003C801E4000003C801E4000003C801E40000078C03E20000078
403C20000078403C200000F0403C100000F02078100000F02078100001F02078080001E010
F0080001E010F0080003E010F00C0003C009E0040003C009E0040003C009E00400078007C0
0200078007C00200078007C002000F0007C001000F00078001000F00078003801F800FC007
C0FFF07FF81FF0>
	 44 32 -1 30 47] 87 @dc
[<
0020004000800100020006000C000C00180018003000300030007000600060006000E000E0
00E000E000E000E000E000E000E000E000E000E00060006000600070003000300030001800
18000C000C00060002000100008000400020>
	 11 46 -3 33 18] 40 @dc
[<
800040002000100008000C00060006000300030001800180018001C000C000C000C000E000
E000E000E000E000E000E000E000E000E000E000E000C000C000C001C00180018001800300
0300060006000C0008001000200040008000>
	 11 46 -3 33 18] 41 @dc
[<
03F0001C3C00200E00400F00400780F00780F807C0F807C0F807C02007C00007C000078000
0780000F00000E00003C0003F000003800001C00000E00000F00000F00000F80380F807807
80780780780F80200F00100E000C1C0003F000>
	 18 31 -2 29 23] 51 @dc

3 @eop0

0 0 3 @bop1 195 w @F3 @sf(The)18 b(sab)q(oteur)g(need)h(not)e(b)q(e)i
(around)f(to)f(giv)o(e)g(the)h(signal)f(to)g(attac)o(k.)27 b(A)18 b
(disgrun)o(tled)g(emplo)o(y)o(ee)f(who)h(w)o(as)-1951 57 y(afraid)d(of)g
(getting)f(\014red,)i(for)f(example,)g(migh)o(t)g(plot)g(his)g(rev)o(enge)h
(in)f(adv)m(ance)h(b)o(y)g(adding)f(an)h(instruction)f(to)-1951 56 y(his)g
(virus)g(that)g(caused)g(it)g(to)g(remain)f(dorman)o(t)h(only)g(so)f(long)h
(as)g(his)g(p)q(ersonal)g(passw)o(ord)g(w)o(as)f(listed)h(in)g(the)-1950 
56 y(system.)k(Then,)14 b(sa)o(ys)f(Cohen,)h(\\as)g(so)q(on)f(as)h(he)g(w)o
(as)f(\014red)i(and)f(the)g(passw)o(ord)f(w)o(as)g(remo)o(v)o(ed,)g
(nothing)h(w)o(ould)-1951 57 y(w)o(ork)g(an)o(y)h(more.")-332 101 y(The)f
(fact)f(that)g(the)h(virus)g(remains)f(hidden)h(at)g(\014rst)f(is)g(what)h
(mak)o(es)f(it)g(so)g(dangerous.)19 b(\\Supp)q(ose)c(y)o(our)e(virus)-1950 
57 y(attac)o(k)o(ed)h(b)o(y)h(deleting)g(\014les)g(in)g(the)h(system,")e
(Cohen)h(sa)o(ys.)20 b(\\If)15 b(it)f(started)h(doing)g(that)f(righ)o(t)g
(a)o(w)o(a)o(y)l(,)g(then)h(as)-1950 56 y(so)q(on)e(as)f(y)o(our)h(\014les)g
(got)f(infected)h(they)g(w)o(ould)g(start)e(to)i(disapp)q(ear)g(and)g(y)o
(ou'd)f(sa)o(y)h('Hey)l(,)g(something's)f(wrong)-1951 57 y(here.')20 b(Y)l
(ou'd)c(probably)f(b)q(e)h(able)f(to)g(iden)o(tify)f(who)q(ev)o(er)i(did)f
(it.")k(T)l(o)c(a)o(v)o(oid)f(early)h(detection)g(of)g(the)h(virus,)e(a)
-1950 56 y(clev)o(er)h(sab)q(oteur)g(migh)o(t)f(add)h(instructions)f(to)h
(the)g(virus)g(program)f(that)g(w)o(ould)h(cause)g(it)g(to)f(c)o(hec)o(k)i
(the)f(date)-1950 57 y(eac)o(h)e(time)f(it)g(ran,)h(and)g(attac)o(k)e
(only)i(if)f(the)h(date)g(w)o(as)f(iden)o(tical)g(-or)g(later)g(than-)h
(some)f(date)h(mon)o(ths)f(or)h(y)o(ears)-1951 56 y(in)i(the)h(future.)k
(\\Then,")15 b(sa)o(ys)g(Cohen,)g(\\one)g(da)o(y)l(,)g(ev)o(erything)g(w)o
(ould)g(stop.)20 b(Ev)o(en)15 b(if)g(they)g(tried)g(to)g(replace)-1950 57 y
(the)i(infected)h(programs)e(with)h(programs)f(that)g(had)i(b)q(een)g
(stored)f(on)g(bac)o(k-up)h(tap)q(es,)g(the)f(bac)o(k-up)h(copies)-1950 
56 y(w)o(ouldn't)c(w)o(ork)g(either)h(-)h(pro)o(vided)f(the)g(copies)g(w)o
(ere)g(made)g(after)g(the)g(system)g(w)o(as)f(infected.)-1676 101 y(The)g
(idea)f(of)g(virus-lik)o(e)f(programs)g(has)i(b)q(een)g(around)f(since)h
(at)f(least)f(1975,)h(when)g(the)h(science)g(\014ction)f(writer)-1951 57 y
(John)18 b(Brunner)g(included)g(one)f(in)g(his)g(no)o(v)o(el)g(`The)g(Sho)q
(c)o(kw)o(a)o(v)o(e)g(Rider'.)26 b(Brunner's)17 b(\\tap)q(ew)o(orm")f
(program)-1951 56 y(ran)21 b(lo)q(ose)g(through)g(the)g(computer)h(net)o
(w)o(ork,)f(gobbling)f(up)i(computer)f(memory)g(in)g(order)g(to)g
(duplicate)-1950 57 y(itself.)30 b(\\It)19 b(can't)g(b)q(e)g(killed,")g
(one)g(c)o(haracter)f(in)h(the)g(b)q(o)q(ok)g(exclaims)g(in)f(desp)q
(eration.)32 b(\\It's)18 b(inde\014nitely)-1950 56 y(self-p)q(erp)q
(etuating)d(as)g(long)f(as)h(the)g(net)o(w)o(ork)g(exists.")-959 102 y(In)j
(1980,)f(John)h(Sho)q(c)o(h)h(at)e(the)h(Xero)o(x)f(P)o(alo)f(Alto)h
(researc)o(h)h(cen)o(ter)f(devised)h(a)g(real-life)e(program)h(that)g(did)
-1950 56 y(somewhat)h(the)i(same)f(thing.)31 b(Sho)q(c)o(h's)20 b
(creation,)f(called)g(a)g(w)o(orm,)g(wriggled)f(through)h(a)g(large)f
(computer)-1950 57 y(system)f(lo)q(oking)g(for)f(mac)o(hines)i(that)f(w)o
(ere)g(not)g(b)q(eing)h(used)g(and)g(harnessing)f(them)g(to)g(help)h(solv)o
(e)f(a)g(large)-1951 56 y(problem.)34 b(It)20 b(could)g(tak)o(e)f(o)o(v)o
(er)g(an)h(en)o(tire)g(system.)34 b(More)19 b(recen)o(tly)l(,)i(computer)f
(scien)o(tists)e(ha)o(v)o(e)i(am)o(used)-1950 57 y(themselv)o(es)d(with)f
(a)h(gladiator)o(ial)o 16 x(com)o(bat,)f(called)h(Core)g(W)l(ar,)g(that)f
(resem)o(bles)h(a)g(con)o(trolled)f(viral)g(attac)o(k.)o -1951 56 a(Scien)o
(tists)h(put)h(t)o(w)o(o)f(programs)g(in)g(the)h(same)g(computer,)g(eac)o
(h)g(designed)h(to)e(c)o(hase)h(the)g(other)g(around)g(the)-1950 56 y
(memory)l(,)c(trying)h(to)f(infect)h(and)h(kill)e(the)h(riv)m(al.)-845 102 y
(Inspired)f(b)o(y)e(earlier)g(e\013orts)g(lik)o(e)g(these,)h(Cohen)g(to)q
(ok)g(a)f(securit)o(y)g(course)h(last)f(y)o(ear,)h(and)g(then)g(set)g(out)f
(to)g(test)-1950 56 y(whether)h(viruses)f(could)g(actually)g(do)g(harm)g
(to)g(a)g(computer)h(system.)18 b(He)13 b(got)f(p)q(ermission)f(to)h(try)g
(his)g(virus)h(at)-1951 57 y(USC)i(on)g(a)g(V)-5 b(AX)15 b(computer)g
(with)f(a)h(Unix)g(op)q(erating)f(system,)h(a)f(com)o(bination)g(used)i(b)o
(y)f(man)o(y)f(univ)o(ersities)-1951 56 y(and)k(companies.)26 b(\(An)17 b
(op)q(erating)g(system)g(is)g(the)g(most)g(basic)g(lev)o(el)g(of)g
(programming)f(in)h(a)g(computer;)h(all)-1951 57 y(other)13 b(programs)f
(use)i(the)f(op)q(erating)f(system)h(to)g(accomplish)f(basic)h(tasks)g
(lik)o(e)f(retrieving)g(information)g(from)-1951 56 y(memory)l(,)i(or)h
(sending)h(it)e(to)h(a)f(screen.\))-695 102 y(In)20 b(\014v)o(e)g(trial)o 
18 x(runs,)h(the)e(virus)g(nev)o(er)g(to)q(ok)g(more)g(than)g(an)h(hour)f
(to)g(p)q(enetrate)g(the)h(en)o(tire)f(system.)32 b(The)-1950 56 y
(shortest)18 b(time)g(to)h(full)f(infection)g(w)o(as)g(\014v)o(e)i(min)o
(utes,)f(the)g(a)o(v)o(erage)e(half)i(an)g(hour.)31 b(In)19 b(fact,)g(the)g
(trial)f(w)o(as)-1951 57 y(so)e(successful)i(that)e(univ)o(ersit)o(y)f
(o\016cials)h(refused)h(to)f(allo)o(w)f(Cohen)i(to)f(p)q(erform)h(further)g
(exp)q(erimen)o(ts.)24 b(Co-)-1950 56 y(hen)d(understands)f(their)g
(caution,)g(but)h(considers)f(it)f(shortsigh)o(ted.)33 b(\\They'd)20 b
(rather)g(b)q(e)h(paranoid)e(than)-1950 56 y(progressiv)o(e,")13 b(he)j
(sa)o(ys.)j(\\They)c(b)q(eliev)o(e)h(in)f(securit)o(y)f(through)h
(obscurit)o(y)l(.")-1343 102 y(Cohen)h(next)f(got)g(a)g(c)o(hance)h(to)f
(try)g(out)g(his)h(viruses)f(on)g(a)g(priv)m(ately)g(o)o(wned)h(Univ)m(ac)g
(1108.)j(\(The)d(op)q(erators)-1951 56 y(ha)o(v)o(e)h(ask)o(ed)f(that)h
(the)g(compan)o(y)g(not)f(b)q(e)i(iden)o(ti\014ed.\))25 b(This)16 b
(computer)h(system)g(had)g(an)g(op)q(erating)f(system)-1950 57 y(designed)g
(for)e(military)f(securit)o(y;)h(it)h(w)o(as)f(supp)q(osed)i(to)f(allo)o
(w)e(p)q(eople)j(with)e(lo)o(w-lev)o(el)g(securit)o(y)g(clearance)i(to)-987 
161 y(3)-987 b
3 @eop1

4 @bop0
@F3 @sf
[<
7FE7FE0700E00700E00700E00700E00700E00700E00700E00700E00700E00700E00700E007
00E00700E00700E00700E00700E00700E00700E0FFFFE00700E00700E00700E00700E00700
E00700E00700E00700E00381E001C1E000E0E0003FE0>
	 23 32 0 31 25] 13 @dc
[<
FFFFFC0F807C07801C07800C07800407800407800607800207800207800207800207800007
80000780000780000780000780000780000780000780000780000780000780000780000780
000780000780000780000780000FC000FFFE00>
	 23 31 -2 30 28] 76 @dc
[<
00FFE0000E00000E00000E00000E00000E00000E00000E00FFFFF0C00E00400E00200E0020
0E00100E00080E00080E00040E00020E00020E00010E00008E00008E00004E00002E00002E
00001E00000E00000E00000600000600>
	 20 30 -1 29 23] 52 @dc

4 @eop0

0 0 4 @bop1 195 w @F3 @sf(share)11 b(a)h(computer)f(with)g(p)q(eople)h
(with)f(high-lev)o(el)f(clearance)i(without)e(leak)m(age)h(of)g(data.)18 b
(But)12 b(the)g(restrictio)o(ns)-1951 57 y(against)e(data)g(\015o)o(w)g
(did)h(not)g(prev)o(en)o(t)g(Cohen's)f(virus)h(from)f(spreading)h
(throughout)f(the)h(system)g(-)g(ev)o(en)g(though)-1950 56 y(he)17 b(only)e
(infected)i(a)f(single)g(lo)o(w-securit)o(y)e(lev)o(el)i(securit)o(y)g
(user.)23 b(He)16 b(pro)o(v)o(ed)g(that)g(milita)o(ry)f(computers,)h(to)q
(o,)-1951 56 y(ma)o(y)e(b)q(e)i(vulnerable,)f(despite)g(their)g
(safeguards.)-877 102 y(The)h(problem)f(of)h(viral)e(spread)i(is)f(comp)q
(ounded)i(b)o(y)f(the)g(fact)f(that)g(computer)h(users)f(often)h(sw)o(ap)f
(programs)-1951 56 y(with)j(eac)o(h)h(other,)f(either)h(b)o(y)f(shipping)h
(them)g(on)f(tap)q(e)h(or)f(disk)g(or)h(sending)f(them)h(o)o(v)o(er)f(a)g
(telephone)h(line)-1950 57 y(or)e(through)g(a)h(computer)f(net)o(w)o(ork.)
26 b(Th)o(us,)18 b(an)g(infection)f(that)g(originat)o(es)f(in)i(one)g
(computer)f(could)h(easily)-1951 56 y(spread)11 b(to)f(others)h(o)o(v)o
(er)f(time)g(-)h(a)g(hazard)g(that)f(ma)o(y)g(b)q(e)i(particularly)d(sev)o
(ere)i(for)g(the)g(banking)f(industry)l(,)i(where)-1950 57 y(informatio)o
(n)g(is)g(constan)o(tly)f(b)q(eing)i(exc)o(hanged)g(b)o(y)f(wire.)19 b(Sa)o
(ys)12 b(Cohen,)h(\\The)f(danger)g(is)g(that)g(someb)q(o)q(dy)h(will)-1951 
56 y(write)g(viruses)g(that)g(are)g(bad)h(enough)g(to)f(get)g(around)h
(the)g(\014nancial)f(institutions)f(and)i(stop)f(their)g(computers)-1950 
57 y(from)h(w)o(orking.")-301 101 y(Man)o(y)22 b(securit)o(y)g
(professionals)f(also)g(\014nd)j(this)e(prosp)q(ect)h(frigh)o(tening.)o 
41 x(Sa)o(ys)f(Jerry)h(Lob)q(el,)i(manager)c(of)-1950 57 y(computer)c
(securit)o(y)f(at)g(Honeyw)o(ell)h(Information)e(Systems)i(in)g(Pho)q
(enix,)g(\\F)l(red)g(came)g(up)g(with)f(one)h(of)g(the)-1950 56 y(more)f
(devious)g(kinds)g(of)g(problems)f(against)g(whic)o(h)h(w)o(e)g(ha)o(v)o
(e)g(v)o(ery)g(few)g(defenses)h(at)e(presen)o(t.")23 b(Lob)q(el,)16 b(who)
-1950 56 y(organized)h(a)g(recen)o(t)h(securit)o(y)f(conference)h(sp)q
(onsored)g(b)o(y)f(the)h(In)o(ternational)e(F)l(ederation)h(for)g
(Information)-1951 57 y(Pro)q(cessing)j(-at)f(whic)o(h)h(Cohen)h(also)e
(deliv)o(ered)h(a)f(pap)q(er-)i(cites)f(other)f(p)q(oten)o(tial)g(targets)g
(for)h(attac)o(k:)o 29 x(\\If)-1950 56 y(it)e(w)o(ere)g(an)h(air)f(tra\016c)f
(con)o(trol)h(system)g(or)g(a)g(patien)o(t)g(monitoring)f(system)h(in)h(a)f
(hospital,)g(it)g(w)o(ould)g(b)q(e)h(a)-1950 57 y(disaster.")-189 101 y
(Marvin)d(Sc)o(haefer,)g(c)o(hief)h(scien)o(tist)e(at)h(the)h(P)o(en)o
(tagon's)e(computer)h(securit)o(y)g(cen)o(ter,)h(sa)o(ys)f(the)h(milit)o
(ary)e(has)-1950 57 y(b)q(een)d(concerned)g(ab)q(out)f(p)q(enetration)f(b)o
(y)h(virus-lik)o(e)f(programs)g(for)g(y)o(ears.)18 b(Defense)11 b
(planners)g(ha)o(v)o(e)g(protected)-1950 56 y(some)k(top-secret)h
(computers)f(b)o(y)h(isolat)o(ing)e(them,)h(just)g(as)h(a)f(do)q(ctor)g
(migh)o(t)f(isolate)g(a)i(patien)o(t)e(to)h(k)o(eep)h(him)-1950 57 y(from)f
(catc)o(hing)g(cold.)22 b(The)16 b(militar)o(y's)e(most)h(secret)h
(computers)g(are)f(often)h(k)o(ept)g(in)f(electronically)g(shielded)-1950 
56 y(ro)q(oms)i(and)h(connected)h(to)e(eac)o(h)h(other,)g(when)g
(necessary)l(,)h(b)o(y)f(wires)f(that)g(run)h(through)g(pip)q(es)g(con)o
(taining)-1951 57 y(gas)f(under)h(pressure.)27 b(Should)17 b(an)o(y)o(one)g
(try)g(to)g(p)q(enetrate)h(the)f(pip)q(es)h(in)f(order)g(to)g(tap)g(in)o
(to)f(the)i(wires,)f(the)-1950 56 y(drop)i(in)f(gas)h(pressure)g(w)o(ould)f
(immediately)f(giv)o(e)h(him)h(a)o(w)o(a)o(y)l(.)29 b(But,)20 b(Sc)o
(haefer)f(admits,)f(\\in)g(systems)h(that)-1951 56 y(don't)14 b(ha)o(v)o
(e)g(go)q(o)q(d)g(access)h(con)o(trols,)e(there)i(really)e(is)h(no)g(w)o
(a)o(y)g(to)g(con)o(tain)f(a)h(virus.)20 b(It's)14 b(quite)g(p)q(ossible)g
(for)g(an)-1950 57 y(attac)o(k)g(to)g(tak)o(e)h(o)o(v)o(er)f(a)h(mac)o
(hine.")-627 101 y(Honeyw)o(ell's)j(Lob)q(el)h(strongly)f(b)q(eliev)o(es)h
(that)g(neither)g(Cohen)g(nor)g(an)o(y)g(other)f(resp)q(onsible)h(exp)q
(ert)h(should)-1950 57 y(ev)o(en)f(op)q(en)f(a)g(public)h(discussion)f(of)g
(computer)g(viruses.)28 b(\\It)19 b(only)e(tak)o(es)h(a)g(halfw)o(a)o(y)e
(decen)o(t)j(programmer)-1951 56 y(ab)q(out)f(half)f(a)h(da)o(y)g(of)g
(thinking)f(to)g(\014gure)i(out)e(ho)o(w)h(to)f(do)h(it,")g(Lob)q(el)g(sa)o
(ys.)28 b(\\If)18 b(y)o(ou)g(tell)f(enough)h(p)q(eople)-1949 57 y(ab)q
(out)d(it,)f(there's)h(going)f(to)h(b)q(e)h(one)f(crazy)g(enough)h(out)e
(there)i(who's)e(going)g(to)h(try)l(.")-1526 101 y(Cohen)i(disagrees,)g
(insisting)f(that)g(it)g(is)h(more)g(dangerous)g(`not')e(to)i(discuss)g
(and)g(study)h(computer)f(viruses.)-1951 57 y(\\The)e(p)q(oin)o(t)g(of)g
(these)g(exp)q(erimen)o(ts,")g(he)g(sa)o(ys,)g(\\is)f(that)h(if)f(I)i(can)f
(\014gure)h(out)f(ho)o(w)f(to)h(do)g(it,)f(someb)q(o)q(dy)i(else)-1950 56 y
(can)f(to)q(o.)k(It's)14 b(b)q(etter)g(to)g(ha)o(v)o(e)g(someb)q(o)q(dy)h
(friendly)g(do)f(the)h(exp)q(erimen)o(t,)f(tell)g(y)o(ou)g(ho)o(w)g(bad)h
(it)e(is,)h(sho)o(w)g(y)o(ou)-1950 57 y(ho)o(w)g(it)g(w)o(orks)g(and)h
(help)f(y)o(ou)h(coun)o(teract)f(it,)f(than)i(to)f(ha)o(v)o(e)g(someb)q(o)q
(dy)h(vicious)f(come)h(along)f(and)g(do)h(it.")k(If)-1950 56 y(y)o(ou)c(w)o
(ait)f(for)h(the)g(bad)h(guys)f(to)g(create)g(a)g(virus)g(\014rst,)g
(Cohen)h(sa)o(ys,)e(then)i(b)o(y)f(the)h(time)f(y)o(ou)g(\014nd)h(out)f
(ab)q(out)-1950 56 y(it,)f(it)h(will)e(b)q(e)j(to)q(o)f(late.)546 376 y(4)
-987 b
4 @eop1

(\nEND-JOB virus.article.dvi\n) print flush
restore