116 lines
5.7 KiB
Plaintext
116 lines
5.7 KiB
Plaintext
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
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³ VIRUS REPORT ³
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³ 1704 Format ³
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ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
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Synonyms: Blackjack, 1704, Falling Letters.
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Date of Origin: September, 1988.
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Place of Origin: Germany.
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Host Machine: PC compatibles.
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Host Files: Remains resident. Infects COM files.
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Increase in Size of Infected Files: 1704 bytes.
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Nature of Damage: Affects system run-time
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operation. Corrupts program or overlay files. Formats or erases
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all/part of the hard disk upon activation.
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Detected by: Scanv56+, F-Prot, IBM Scan, Pro
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-Scan.
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Removed by: CleanUp, M-1704, Scan/D, F-Prot.
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Derived from: 1701 (Cascade) virus.
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Scan Code: Uses self-encryption. FA 8B EC E8
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00 00 5B 81 EB 31 01 2E F6 87 2A 01 01 74 0F 8D B7 4D 01 BC
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85 06 31 34 31 24 46 4C 75 F8.
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The code for the 1704 virus is identical to the 1701 except for a
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single instruction. The only differences are the removal of a
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conditional jump from the 1701 (which would never have been taken), and
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some necessary segment overrides on the BIOS tests missing in the
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previous version. The virus was designed to not infect micros
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manufactured by IBM, but errors in coding enable it to infect any PC,
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regardless of origin. The virus tests the BIOS for the string "COPR.
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IBM", and contains code to not infect if it finds this - however there
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are errors in the code which prevent it from working.
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As with the 1701, the 1704 can recognize if it has previously
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infected a file. However, because recognition depends on the length of
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the virus, it will infect programs already infected by variants with
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different lengths. (1701 will infect COM files infected with 1704, and
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vice versa.)
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The encryption of this virus is different in each instance of the
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virus, being dependent on the size of the host file.
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The hard disk is formatted when the virus activates.
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This virus has been termed "Blackjack", which is a pun on the German
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name "17+4" of a popular card game.
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Blackjack infects only COM-files which are at least 3 bytes long, and
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it does so only once for any given file. It overwrites the first three
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bytes with a JMP to the beginning of the viral code, which is appended to
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the file. The 2 byte address of this JMP instruction is probably the
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reason why only COM files are susceptible to infection. Blackjack
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retains the file's time stamp. It even infects read-only files; on
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write-protected floppy disks, it attempts writing 5 times per file, thus
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revealing its activity.
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In the infected file, the viral code is cryptographically encoded,
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using a simple Vigenere code depending on the length of the file; only
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the instructions for decoding the encrypted part of the code are in plain
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machine-language. This is obviously intended as a impediment against
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disassembling. Hence, every copy of the virus looks different
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(depending on the length of the file).
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On invocation of an infected program, Blackjack installs itself in
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RAM (if no copy is already installed), then replaces the JMP instruction
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with its former contents and resumes normal program operation.
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The storage map shows that Blackjack has tinkered with the free
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storage pointer-chain to hide the fact that it has hooked interrupt 21.
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Hence, only a minor part of Blackjack is visible in the storage map.
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In every year, from October to December, Blackjack will interfere
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with CGA or EGA operated screens, moving randomly chosen characters
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down, like falling leaves in autumn. After a while, you'll have a big
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heap of characters at the bottom of your screen, and as you cannot see
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anymore what the computer is trying to display, you'll probably have to
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restart the system. This behaviour has been predicted by two people, who
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have disassembled Blackjack, and has later been observed on many
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EGA-equipped ATs.<Note: Contributions to this section by Otto Stolz.>
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ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
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º This document was adapted from the book "Computer Viruses", º
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º which is copyright and distributed by the National Computer º
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º Security Association. It contains information compiled from º
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º many sources. To the best of our knowledge, all information º
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º presented here is accurate. º
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º º
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º Please send any updates or corrections to the NCSA, Suite 309, º
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º 4401-A Connecticut Ave NW, Washington, DC 20008. Or call our BBS º
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º and upload the information: (202) 364-1304. Or call us voice at º
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º (202) 364-8252. This version was produced May 22, 1990. º
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º º
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º The NCSA is a non-profit organization dedicated to improving º
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º computer security. Membership in the association is just $45 per º
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º year. Copies of the book "Computer Viruses", which provides º
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º detailed information on over 145 viruses, can be obtained from º
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º the NCSA. Member price: $44; non-member price: $55. º
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º º
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º The document is copyright (c) 1990 NCSA. º
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º º
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º This document may be distributed in any format, providing º
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º this message is not removed or altered. º
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ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
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