Nov 13, 2013

What are symptoms that indicate my PC is infected with malware or viruses?

My laptop has slowed to the point of being painful to use. It’s a few years old, so perhaps it’s just that, but how can I make sure it isn’t infected with malware or a virus. I have AVG anti-virus and ran a full system scan and didn’t find anything. What are typical symptoms of an infected machine?

What are the symptoms of an infected computer?


Your computer behaves strangely, i.e. in a way that you haven’t seen before.

You see unexpected messages or images.

You hear unexpected sounds, played at random.

Programs start unexpectedly.

Your personal firewall tells you that an application has tried to connect to the Internet (and it’s not a program that you ran).

Your friends tell you that they have received e-mail messages from your address and you haven’t sent them anything.

Your computer ‘freezes’ frequently, or programs start running slowly.

You get lots of system error messages.

The operating system will not load when you start your computer.

You notice that files or folders have been deleted or changed.

You notice hard disk access (shown by one of the small flashing lights) when you’re not aware of any programs running.

Your web browser behaves erratically, e.g. you can’t close a browser window."
  • Task manager shows a high CPU when you think your machine should be idle (e.g. <5%).
  • Advertisements popping up at random.


    2. Virus warnings popping up from an antivirus that you didn't intentionally install (the antivirus program is a fake and tries to claim you have scary sounding viruses with names like 'bankpasswordstealer.vir'. You're encouraged to pay for this program to clean these).


    3. Web pages redirected or blocked, for example, home pages of AV products or support sites (www.symantec.com, www.avg.com, www.microsoft.com) are redirected to sites filled with adverts, or fake sites promoting bogus anti virus / "helpful" removal tools, or are blocked altogether.

    Increased startup time


    4. Random failures and things happening when they shouldn't (e.g. some new viruses put group policy restrictions on your machine to prevent task manager or other diagnostic programs from running).


    Slow performance certainly is one of them. Others include when your computer freezes, mystery icons show up on your desktop, you get messages about corrupted files, and you are unable to access some maintenance and repair tools.

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