How Do I Know if My Computer Is Infected with Malicious Software?

There are some common signs that may indicate your computer has become infected with malicious software - whether its adware, spyware, trojans, viruses, or some other form of exploit.

Look for these symptoms:

  1. You are the only user on your computer but there are changes you didn’t make - like your home page is different, there’s a new toolbar you didn’t install, favorites have been added to your browser, your default browser or search engine has changed, your default language has changed, and so on.
  2. Your computer quits running and barely crawls. Slowdowns can be a sign of malware, especially if you aren’t having network issues and haven’t downloaded a big program and don’t have multiple programs running at the same time. If you look at your task manager and there are all kinds of system resources being used for things you aren’t doing, you’re probably infected.
  3. You begin getting lots of pop-ups ads even when you aren’t on the internet. One especially nasty variety is a popup ad warning you that your computer is infected and instructing you to click on the offered antivirus (it’s fake) to protect your computer - NEVER click anywhere on this popup as any click will give you more trouble. Instead shut down the pop-up through your task manager.
  4. Files disappear or are changed. First, be sure you didn’t misfile things, but if files are disappearing or the authorship has changed you are probably infected. If you can see your files but can’t access them you may have ransomware - malicious software that hijacks access until you pay the extortionist (don’t do it, you still won’t get access). This is another good reason to automatically back up your files daily.
  5. Your computer won’t boot up, won’t connect to the internet (or connects with a whole bunch of windows open to sites you didn’t go to), won’t perform basic functions, randomly shuts down, or does other weird things. You are probably infected.
  6. Your computer sends email that you aren’t generating. You are probably infected and probably part of a botnet.
  7. You had an anti-virus program but it disappeared. You are probably infected - especially if all your security tools are disabled or have vanished. Many malware threats target the security systems first so they can wreak havoc without being hampered.
  8. You can’t get your applications to open or run, or clicking on one application icon actually opens something else. Yep, you are probably infected.
  9. Typing in a URL to a specific website takes you somewhere else. You are probably infected.
  10. You don’t notice anything wrong with your computer. Unfortunately, a lot of malware is specifically designed to go undetected, so while the previous nine points are important to look for, you may be infected without knowing it.

Your best bet is to always practice these 4 simple steps to increase your malware resistance:

  1. Ensure your computers are up-to-date with all available patches, fixes, and upgrades. If you do not have your operating system set up to automatically update, do so now. To learn how, go to your operating system’s website and follow their instructions – look here for Windows users, and here for Mac Users.
  2. Confirm that your browsers are up-to-date. The easiest way is to download the latest versions. Download Firefox versions here. Download IE versions here. Download Google Chrome versions here.
  3. Check your computer’s security software. It should be up-to-date with all available patches, fixes, and upgrades. Click on your security program’s icon and see if it tells you that you need to update your program. If you don’t have security software installed - INSTALL SECURITY SOFTWARE NOW.

    Check your phone’s security software. If you are using as smartphone, you need to have security software installed. Mobile malware has come to stay, and unprotected phones are vulnerable to exploits.

  4. Strengthen your Spam protection: This takes setting your email spam filters to an appropriately high level, and some smartening up on your part. Every email program has spam filters. To find yours, look under your settings options, and set these high - just remember to check your spam folder periodically to see if legitimate email has been accidentally trapped there. You can also search for a step-by-step guide to setting your spam filters by searching on the name of your email provider plus the phrase ‘spam filters’.

    Smarten up about Spam, social engineering, phishing and scams: Spam and scams come at us from all angles; in the mailbox in front of your home (junk mail) in your email inbox, via IM, social networking sites, chats, forums, websites, and sadly, now also on your phone.

    • You do not have a rich uncle you’ve never heard of in some foreign country trying to send you money. You have not won the lottery. No stranger is going to give you money for any reason. No hot babe is lonely and waiting for your response. The only things you’ll get via an unsolicited pharmacy offer is ripped off or an infection (on your computer or phone). If there really was a miracle weight loss cure, it would be front page news and on every TV station.
    • No reputable bank or company is ever going to ask you to ‘authenticate’ information online. And if you get an email with a link to one of these sites, don’t use it; instead, use your search engine to find the site yourself, and then log in. If the message was legitimate, the message will be waiting for you in your account.
    • Do not open attachments or download anything without knowing who sent these to you, and you are expecting them. Email account hacking has become so prevalent that though the email, link and attachment appear to be from a friend, it could be from the hacker who has taken over your friend’s account.

These steps cannot guarantee you will never fall victim to a new aggressive malware exploit, but they will keep your much safer.

Provided by Linda Criddle, Founder of