A computer virus is a software program which is able to self-copy from one infected object to other objects (objects can be program files, document files, etc.). After infecting a computer, it may slow down the computer performance; damage the infected files, cause data loss and system errors, etc.
Virus may also use victims' computers for illegal ads, spams; disturb computer users, reduce information security level; steal personal information, account information, credit card number, etc. Some viruses even take advantage of victims' computers to form botnets (zombie computer network) to attack server systems or websites, etc.
Followings are some signs when your computer has been infected with viruses:
- Ad-sites automatically pop-up, Desktop background is modified.
- A small symbol with notification "Your computer has been infected…" or "Virus Alert" appears at Desktop's bottom right corner.
- Browser's homepage is changed to an exotic one.
- Suspected files (Autorun.inf, New Folder.exe…) are automatically generated when you open an USB drive.
- Files with .exe extension appear with the same names as your folders.
Besides, there are many viruses running in background along with systems without any special or abnormal signs. So, it is really hard for computer users to know if their computers have been infected or not.
Thus, to secure your computer, you should choose good antivirus software to install for a long-term usage on your computer. A good antivirus software should acquires the following criteria: a licensed software, update on regular basis, direct support from vendor for virus problems.