How viruses activate

We are always afraid that viruses do something harmful to files when they get active, but not all the viruses activate. Some viruses just spread out but when viruses activate they do very different things. Might play a part of melody or play music in the background, show a picture or animated picture, show text, format hard disk or do changes to files.

As an example, in one unnamed company: over a long period of time, the files in a server were corrupted just a bit. So backup copies were taken from the corrupted files. And after they noticed that something was wrong, it was too late to get back the data from the backups. That kind of event is the worst that can happen for the uses.

There is also talk that viruses have done something to hardware like hard disk or monitor.

Viruses can not do any harm to hardware but they can do harm to programs and tor example to BIOS so that computer does not start after that. Usually you can start the computer from a boot

diskette in the computers doesn’t start otherwise.

2.6 Viruses in different platforms

2.6.1 PC viruses

Viruses are mostly written for PC-computers and DOS environment. Even though viruses are made for DOS environment, they are working also in Windows, Windows95, Windows NT and OS/2 operating systems. Some viruses like boot sector viruses, do not care what about operating systems.

2.6.2 Macintosh viruses

Macintosh viruses are not as a big problem as PC viruses are. There are not so many viruses in Macintosh operating system. Macintosh viruses has been found mostly from schools.

How many Mac viruses there are? I found out that there are about 2-300 Mac-specific viruses. There are virtually no macro viruses which have a Mac-specific payload, but all macro viruses can infect on Macs and other platforms which runs Word 6.x of better.

2.6.3 Other platforms

Viruses can be found from in almost any kind of computer, such as HP calculators used by students like HP 48-calculators and old computers like Commodore 64 and Unix computers too. In general, there are virtually no non-experimental UNIX viruses. There have been a few Worm incidents, most notably the Morris Worm,, the Internet Worm, of 1988.

There are products which scan some Unix systems for PC viruses. Any machine used as a file server (Novell, Unix etc.) can be scanned for PC viruses by a DOS scanner if it can be mounted as a logical drive on a PC running appropriate network client software such as PC-NFS. Intel-based PCs running Unix e.g. Linux, etc. can also be infected by a DOS boot-sector virus if booted from an infected disk. The same goes for other PC-hosted operating systems such as NetWare.

While viruses are not a major risk on Unix platforms, integrity checkers and audit packages are frequently used by system administrators to detect file changes made by other kinds of attack.

3. How to deal with viruses

3.1 What are the signs of viruses

Almost anything odd a computer may do, can blamed on a computer "virus," especially if no other explanation can readily be found. Many operating systems and programs also do strange things, therefore there is no reason to immediately blame a virus. In most cases, when an anti­virus program is then run, no virus can be found.

A computer virus can cause unusual screen displays, or messages - but most don't do that. A virus may slow the operation of the computer - but many times that doesn't happen. Even longer disk activity, or strange hardware behavior can be caused by legitimate software, harmless "prank" programs, or by hardware faults. A virus may cause a drive to be accessed unexpectedly and the drive light to go on but legitimate programs can do that also.

One usually reliable indicator of a virus infection is a change in the length of executable (*.com/*.exe) files, a change in their content or a change in their file date/time in the Directory listing. But some viruses don't infect files, and some of those which do can avoid showing changes they've made to files, especially if they're active in RAM.

Another common indication of a virus infection is a change to the reassignment of system resources, unaccounted use of memory or a reduction in the amount normally shown tor the system may be significant.

in short, observing "something funny" and blaming it on a computer virus is less productive than scanning regularly for potential viruses, and not scanning, because "everything is running OK"

Is equally inadvisable.

3.2 What to do when you find viruses?

First thing what you should do when you find virus is count to ten and stay cool. You should keep notes on what you do and write down what your virus programs and you computer tells you. If you are not sure what to do, you should call the administrator for future action. In some cases it is not good to start you computer from hard disk, because the virus may active and then do some harm.

Second, make sure that you should get sure that it is virus and what virus it is. It is important to know what kind of virus we are dealing with. Companies that make anti-virus programs knows what different viruses does and you can ether call them and ask about that viruses or you can go to their web pages and read about the virus you have.

When you start you computer you should do it from a clean (non-infected) floppy diskette and after that run the virus program. The boot diskette should be write protected so that virus can not infect the boot diskette too.

It is good to take a backup of the file that was infected. Virus program could do some damage to the file and that is why it is good to have a backup.

It is good to let you administrator to know about the virus, so viruses would not spread around so much. In TKK PC classes are protected by anti-virus program and that virus program reports to a person, responsible for virus protection.

4. How to protect from viruses

4.1 How to provide against viruses

Best way to protect yourself is to prepare your computer against viruses in advance. One way to protect you computer is to use updated anti-virus program. When you get an email attachment, you should first check the attachment by checking the file with a anti-virus program.

As an example in one unnamed Finnish company all information was mailed in email attachments. There was this one Word document that was mailed to everybody. That email attachment was infected by a macro virus. Everyone got the infected attachment and those who opened that attachment by Word got that САР-macro virus. After all there were a few thousand infections. It took lots of time and money to clear that virus.

One can protect the computer against boot sector viruses by setting the BIOS to start from a hard disk rather than from a floppy disk.

Write protection is a good way to prohibit against viruses. Write protection works well in floppy disks, Windows NT and UNIX, but not that well in Windows and Windows95.

Date: 2014-12-29; view: 1044