AVG has produced the following guide of the 10 most common symptoms of computer infection:1. When computer is running unusually slowly.
If a PC has been infected by a virus, worm, Trojan or some other form of malware, it could be running tasks that consume a lot of resources, making the system run more slowly than usual.
2. When computer keeps popping up messages. If pop-ups and messages appear on the desktop, either advertising things or saying that the PC is infected, the computer probably has a malware infection. Spyware or adware is also commonly used as well as fake anti-virus programs (also called "rogueware") to deceive the user into parting
with financial details.
3. When connect to the Internet, windows open or my browser displays web pages I have not requested. Many threats are designed to redirect traffic to certain web sites against the user's will, and can even cause browsers to display spoof web pages. Normally this happens when looking for something in a search engine or when
typing a URL into an address bar. The user presumes they have opened a legitimate website when really they have been taken to a malicious imitation. The free AVG LinkScanner on Windows or Mac computers will help protect from these web pages.
4. When you cannot connect to the Internet or it runs very slowly. Loss of Internet communication is another common symptom of malware infection. This problem could also be due to the Internet service provider (ISP) or modem router. If a computer has been infected, the malware could be connecting to a URL or opening separate connection sessions, thereby reducing available bandwidth.
5. When anti-virus has disappeared, firewall is disabled. Another typical characteristic of malware threats is
that they disable the security software already installed on computers. If one security protection layer shuts down it might be a specific software failure. However, if all security components are disabled, the computer is infected.
6. Applications won't start or the computer keeps crashing. This is when infection causes applications from the start menu or desktop to stop working and other programs to run. This could either be caused by an update or poor installation process or if the computer unexpectedly or erratically crashes persistently then it may be due to malware. This especially happens when trying to open up a security program, or trying to fix malware problems.
7. When computer has new programs. If there are new programs on the computer's desktop that have been downloaded and installed without consent or knowledge, it's likely the computer is infected. Usually these programs have explicit or illegal content and it's near impossible to delete them like a normal program.
8. Where have files gone? There are malware threats designed to delete or encrypt information. Others move documents from one place to another. Some remove the library files for running games, security software and other programs. If a computer is in this situation, it's highly likely to be infected.
9. When computer is speaking a strange language. Certain infections cause the language of certain applications to change or the screen to appear back-to-front.
10. When computer has a mind of its own. If the computer starts acting on its own or sends emails without your knowledge, it is infected. Other signs include Internet sessions or applications opening sporadically.
