Below is a list of common symptoms that may indicate your computer has been infected with a virus.
Crashing, freezing and general slowness
If your computer has been running fine and then suddenly begins to crash, freeze up for long periods of time and exhibit overall slowness, chances are you have contracted a computer virus. While some misconfigured hardware or software might also cause this behavior, those symptoms tend to happen right after you have intentionally made a modification. Viruses can often run tasks that eat up your system resources which results in your system running slower than usual. Try to identify what process or program is eating up your resources by running the Windows Task Manager.
Are you receiving pop-up messages even though you are running a pop-up blocker in your web browser? Most modern browsers (Chrome, Firefox, IE, Safari) include robust pop-up blockers, so pop-ups shouldn’t be a regular occurrence if you browser is up-to-date. It is time to be concerned if you are still receiving pop-ups even while none of your Internet browsers are open. Most of these pop-ups claim that your computer is infected with a virus and that you should download xyz software to fix it. Don’t download their recommended software, as it will just install more malware!!! Instead, download a reputable malware removal program such as MalwareBytes.
Hijacked email accounts – reports of messages that you did not send
Some viruses or malware will send emails containing malicious links to contacts in your address book. These messages may sometimes be detected by your email system administrator who happens to notice and unusual amount of email originating from your account, but more than likely you’ll find out because one of your security savvy friends will let you know they received a suspicious email from your address. What do you do if your email account has been compromised… change your password immediately! You may also want to alert your contacts that a malicious email was sent out from your account. Proceed to doing a full virus scan on your computer.
Warnings that your computer has been locked
Some malware masquerades as official looking notices from federal agencies such as the FBI or the CIA informing you that your computer has been locked due to some illegal activity (see example screenshots below). The notice warns that you must pay a fine to unlock your computer or you will be arrested. These fines are only payable through untraceable MoneyPaks. This type of malware is known as ransomware written by cybercriminals looking to make a fast buck at your expense. Even after paying the money, these warnings remain. If you encounter one of these viruses, do NOT pay to have your computer unlocked. Instead, take your computer to to the ITS Help Desk to see if your files are recoverable.
Essential functions don’t work
Some viruses prevent essential functions from launching such as anti-virus software, the Windows task manager or other applications. Viruses often try to block your anti-virus software from receiving the latest updates as a way defending its own existence. You will likely have install another malware removal tool such as MalwareBytes to remove these threats. Often times, you may need to use more than just one tool to rid your computer of a virus. If your computer suffers a severe virus infection, re-installing your operating system may be the only wan to ensure you computer is virus-free.