Top 10 guide to common symptoms of infection of viruses, malware or Trojans
AVG (AU/NZ) has produced the following simple guide to the ten most common symptoms of infection. You can use it to determine if your computers are already infected:
My computer is running unusually slowly. This could be a symptom of many things, including infection by malware. If your PC has been infected by a virus, worm, Trojan or some other form of malware which is now running on the computer, it could be running tasks that consume a lot of resources, making your system run more slowly than usual.
My computer keeps popping up messages. Your computer has all types of pop-ups and messages on the desktop, either advertising things or saying that the PC is infected and that you need to pay for protection. This is a typical sign of a malware infection. There is either spyware or adware on the computer, or it has been infected by a fake anti-virus program (also called "rogueware"). The bad guys use this technique so once you're infected with malware, they can deceive you into giving them your financial details. Typically they'll also give you a false anti-virus program which is just more malware.
When I connect to the Internet, all types of windows open or my browser displays web pages I have not requested. This is another certain sign of malware infection. Many threats are designed to redirect traffic to certain web sites against the user's will, and can even cause your browser to display spoof web pages. Normally this happens whilst looking for something in a search engine or when you type a URL into an address bar. You think you are on a legitimate web site when really you have been taken to a malicious imitation. The free AVG LinkScanner on your Windows or Mac computer will help to protect you from these nasty web pages.
I cannot connect to the Internet or it runs very slowly. Loss of Internet communication is another common symptom of malware infection. But please keep in mind that this problem could also be due to a problem with your Internet service provider (ISP) or modem router. You might also have a connection that runs much more slowly than usual. If you have been infected, the malware could be connecting to a URL or opening separate connection sessions, thereby reducing your available bandwidth or making it practically impossible to use the Internet.
My anti-virus has disappeared, my firewall is disabled. Another typical characteristic of many malware threats is that they disable the security software already installed on computers. If just one security protection layer shuts down it might just be a specific software failure. However, if all of your security components are disabled, your computer is almost certainly infected.
Applications won't start or the computer keeps crashing. How many times have you tried to run an application from the start menu or desktop and nothing happens? Sometimes another program might even run. This could be another type of problem caused by an update or poor installation process, but at the very least it's a symptom which tells you that something is wrong. Also, if your computer unexpectedly or erratically crashes persistently then it may be due to malware. This will normally happen when you try to open up a security program, or try to find a solution to fix the malware problem.
My computer has new programs. If there are programs on your desktop that you have never seen before, that have been downloaded and installed without your consent or knowledge, then it's more than likely down to malware taking over your computer. Usually these programs have explicit or illegal content and it's near impossible to delete them as you would with a normal program.
Where have my files gone? Hopefully you will be never asking this type of question. However, there are still some malware threats around 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 you find yourself in this situation, it's highly likely your computer is infected.
My computer is speaking a strange language. If the language of certain applications changes or the screen appears back-to-front... you might just have an infected computer system.
My computer has gone crazy. It's likely your system could be compromised by malware if the computer starts acting on its own or you suddenly find your system has been sending emails without your knowledge. Other signs include Internet sessions or applications opening sporadically on their own.
Jump over to our free software section and download a copy of AVG free. For better protection and piece of mind, Techtalk recommends AVG Internet Security 2011 to be installed.