| What are computer viruses?
A computer virus is a self-replicating program containing code that explicitly copies itself and that can "infect" other programs by modifying them or their environment such that a call to an infected program implies a call to a possibly evolved copy of the virus.
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What is a Trojan Horse?
A TROJAN HORSE is a program that does something undocumented that the programmer intended, but that some users would not approve of if they knew about it.
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What are the symptoms and indications of a virus infection?
Many people associate destruction--file corruption, reformatted disks and the like--with viruses. Machines infected with viruses that do this kind of damage often display such damages too. This is unfortunate, as usually viruses can be detected or prevented from infecting long before they can inflict any (serious) damage, though many viruses have no "payload" at all. Note that viruses that simply reformat the hard disk shortly after infecting a machine tend to wipe themselves out faster than they spread, so don't get far.
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What steps should be taken in diagnosing and identifying viruses?
Most of the time, a virus scanner program will take care of that for you. To help identify problems early, run a virus scanner:
- On new programs and diskettes (write-protect diskettes before scanning them).
- When an integrity checker reports a mismatch.
- When a generic monitoring program sounds an alarm.
- When you receive an updated version of a scanner (or you have a chance to run a different scanner than the one you have been using).
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Could an anti-virus program itself be infected?
Yes, so it is important to obtain this software from good sources, and to trust results only after running scanners from a "clean" system. But there are situations where a scanner appears to be infected when it isn't.
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Does a write-protect tab on a floppy disk stop viruses?
In general, yes. The write-protection on IBM PC (and compatible) and Macintosh floppy disk drives is implemented in hardware, not software, so viruses cannot infect a diskette when the write-protection mechanism is functioning properly.
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Can a virus hide in a PC's CMOS memory?
No. The CMOS RAM in which PC system information is stored and backed up by batteries is accessible through the I/O ports and not directly addressable. That is, in order to read its contents you have to use I/O instructions rather than standard memory addressing techniques.
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Can I contract a virus on my PC by performing a "DIR" of an infected floppy disk?
Assuming the PC you are using is virus free before you perform the DIR command, then the answer is "No".
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Can I get a virus from reading e-mail, BBS message forums or USENET News?
In general terms, the answer is no. E-mail messages and postings on BBSes and News are text data and will not be executed as programs. Computer viruses are programs, and must be executed to do anything, so the simple act of reading online messages doesn't pose a threat of catching a computer virus.
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