How you know you have malware on your PC
Original post 8/8/2015
Updated 02/4/2020

The idea for this article came from PC Magazine at http://www.pcmag.com.
Read the original article here.

    If your computer is running erratically or has suddenly slowed down for no apparent reason it may have malware jamming up its works.

Everyone is at risk
    In years past, whenever anyone complained about the insidious problems of malware infecting their Windows PC there would be the inevitable refrain from Mac users, "My Mac is secure, it doesn't get viruses." Unfortunately Mac users can't say that anymore. Witness the outbreak a few years ago of the fake antivirus called Mac Defender which attempts to bilk Mac users out of the hard-earned cash by selling a cure for the horrid popups on their internet browsers, caused by what? Mac Defender, of course.
    Then there's the recent news of an Android malware vulnerability called Stagefright.
    These examples are made not to criticize other operating systems, but to point out that if you go online with an electronic device you are at risk and you need to take the proper precautions.

    Read on to see the nasty things malware can do to your PC if you don't have a good antivirus programs suite running on your computer. If you see anything like the following scenarios you should immediately run Malwarebytes; that is, if you can still update it or even access it.

Popup ad windows open without the browser
    Adware programs bombard you with all types of unwanted information. Occasionally they're ads for legitimate products, but mostly they contain links to malicious websites that will try to put more malware on your PC.

Your search sites have changed.
    Clicking on Google takes you to an different search site. However, this redirection may take a more dangerous turn.
    You may be redirected to a fake banking site that looks just like your bank's real site. If you look at your internet address (URL) you find that it's not secure.
    Your bank's site has a https prefix in its internet address rather than http. A https prefix indicates a secure internet site where you can do business with confidence. If it doesn't you can be fairly certain the site is bogus.

A bogus antivirus program that you never installed generates scary warnings.
    A fake antivirus program with a name like Live Security Professional, Attentive Antivirus, or System Doctor generates popups that warn you of malware on your PC. In reality the malware is the program that is generating these popups. The program will inevitably require payment up-front to remove the made-up malware.
    When, and if, you pay the malware seems to instantly go away, for a while. But then it will almost always come back demanding another payment.

You may find posts you didn't write on your social media pages.
    Malware on social media sites like Facebook creates bogus posts. Simply clicking on these posts may initiate a malicious download to your PC. Malware like this is hard to avoid. If you have no active antivirus program running your PC will be infected and you may pass it along without even knowing it.

You find you cannot use common system tools and utilities.
    Tools like Task Manager, System Restore, MSConfig, and even RegEdit are suddenly unavailable. Trying to use these utilities may trigger a message saying your PC administrator has disabled them. Some malware will disable these tools as an act of self-defense to make it hard for you to eliminate the infection.

You cannot update the virus definitions for your installed and/or registered anti-virus/anti-malware programs because of an unexpected error. Cause may be unspecified.
    Legitimate programs that may be affected: Windows Defender, Microsoft Security Essentials, or any legitimate third-party anti-virus program such as Norton Antivirus, Macafee, Avira, Trend Micro, Panda, Kaspersky, AVG, Avast, etc. Even legitimate scanners such as Malwarebytes may be affected.

Finally, perhaps one of the most scary threats
    Ransomware blatantly announces that your files are encrypted and a payment is required to release them back to you.
    This could also be in the form of a fake FBI or United States Courts program that takes control of your files on your PC.
    This ransomware displays a lock screen that does not allow you to access your Windows desktop or your files until you pay a fine to get them back.

    Unfortunately, even if you pay there is no guarantee that you will get control of your computer or your files back.

    The only sure way to get your files and the use of your computer back is to keep a recent backup of your important files on a disk not normally connected to your PC.
    This could be as simple as keeping recent copies of your important files on a USB Flash Drive or as complete as a full disk image of the hard drive of your computer.
    Of course the hard drive in your computer must be completely formatted before restoring any files. (If no disk image is available the operating system (Windows) must be reinstalled also.)
See this page for more information about backups.

If any of the above situations exist on your PC then you know you have a virus or malware present on your PC and you need help!

If you wish to attempt a fix yourself - See the Malware removal section of our page Is your PC running Sloowly Now? for recommended software remedies.
    You can also go to Bleeping Computer website if you wish to view tutorials for self-help.
    Note: You may need to do this on another non-infected PC.

If none of this helps to remedy your situation contact us or any good PC technician.

What you can do before you get malware
    Don't ignore update notices or warnings generated by your antivirus program. Also be aware that all programs of this type require periodic (at least annual) software updates which you may need to authorize.
    In addition, you can check the status of your installed antivirus software on a regular basis by clicking its icon located in the taskbar.
    Note: Good active antivirus software has a feature which downloads virus definition files periodically (usually daily) from the software vendor's site if you have an active internet connection.
    If the antivirus software that came with your PC is no longer active because you didn't pay (lapsed subscription) your PC is not protected!

Fortunately there is no need to spend a lot of money for a good antivirus program.
Avast Free Antivirus, and AVG Free Antivirus are good free ones. Download one of them from FileHippo.com or use Ninite.com to easily install the one you choose.
    Other free alternatives are Panda Free Antivirus, Bitdefender Free Antivirus and Kaspersky Free Cloud Antivirus.

    However if you feel that paying for an antivirus program is preferable then get Norton Antivirus. Norton has consistently received a top rating by experts from CNET, PC Magazine and PC World Magazine. BitDefender, Kaspersky and McAfee are other top-rated choices.
    Note: All paid antivirus software is subscription based. You must pay on a periodic basis to keep the software active.

If you have a Apple Mac PC see this Page for AntiVirus Suggestions.

Follow the suggestions on this page to avoid malware infestation.

    Download and install the free version of Malwarebytes virus/malware scanner. Run it occasionally (after updating the virus definitions).
    This is an excellent program that can detect and remove malware that may slip past your active antivirus program. It happens!

    Unfortunately there is no antivirus software in existence that will provide complete, 100% protection against all forms of malware. Good browsing technique and being careful when downloading software from the internet are good habits to develop.
    And don't ignore the warnings or notices from your antivirus software!

For More Info:
    See my file Freeware for more information.
    Also see my Security Programs Page for links to all major Security (Antivirus) vendor's sites as well as my recommendations for Active Antivirus programs for your Windows PC. Both Free and Paid (subscription based) programs are listed.

Remember, if you don't have an active security program running on your Windows PC you are at RISK!