Sometimes even an experienced user may not realize that his computer has been infected with a virus. This happens when viruses are hidden among ordinary files or mask themselves in the form of standard files. This section contains a detailed discussion of symptoms of virus infection, shows how to recover data after a virus attack and how to prevent data corruption by malicious programs.
Signs of infection
The computer infection can indicate many signs. If ‘strange things’ like the ones described below occur with the computer, there is a high probability that an infection has occurred:
- sudden display of messages or images,
- the appearance of randomly selected sounds or music,
- mysterious opening or closing of CD-ROM drives,
- sudden launching of programs on the computer,
- notification of a firewall that some applications attempt to connect to the Internet without initiating this action by the user.
The following events are typical signs of a computer infection via e-mail:
- friends or co-workers say they have received messages they have not sent,
- the mailbox contains many messages that do not have the sender’s e-mail address or header.
- However, these problems are not always caused by the presence of a virus. For example, infected messages allegedly coming from a user’s address may in fact be sent from another computer.
The computer infection may also indicate a number of other, secondary signs:
- frequent blocking of the computer or errors,
- slow down the computer when running programs,
- unable to load the operating system,
- disappearing of files and folders or changing their contents,
- too frequent access to the hard disk,
- blocking or unforeseen behavior of Microsoft Internet Explorer, e.g. you can not close the application window.
- In 90% of cases, the listed signs indicate hardware or software problems. Although it is unlikely that they are caused by a virus infection, it is recommended that you perform a full computer scan.
What should you do if you have signs of infection?
If the computer behaves in an unpredictable way:
- Do not panic! In this way, you can avoid losing important information stored in your computer and unnecessary stress.
- Disconnect the computer from the Internet.
- If the computer is connected to a local area network, disconnect it.
- If you can not start your computer from the hard disk (error on startup), try to boot into safe mode or using the Windows startup disk.
- Before taking any action, copy all important data to an external disk (floppy disk, CD, flash memory, etc.).
- You must install an antivirus program if it is not already present in the system.
- Download the latest updates of anti-virus databases. If possible, do not download databases using an infected computer, but use a friend’s computer or located in the office, internet cafe, etc. This is important because if the infected computer is connected to the Internet, the virus can send important data to third parties or try to send to all addresses contained in the address book. Updates of the antivirus program can be obtained on the CD-ROM from the antivirus software vendor or an authorized distributor.
- Perform a full system scan.