It sucks to be constantly bombarded by computer-related threats, whether they’re spyware, malware, viruses, keyloggers, or whatever else. A popular way to combat this problem is to install an antivirus solution that sits in the background and keeps you safe. But no matter what resident solution you’re using, it might not catch each and every infection. That’s where the one-time-scanner steps in.

I am a big fan of one-time-scanners because you can scan whenever you want. Instead of being surprised by a system scan that lags everything down, you can plan your activities and fit the virus scan in where it’s most convenient for you. You may not need a daily defender; instead, a manual weekly scan may be enough for you.

So if you’re looking for the best online antivirus scan and anti-malware tools that free can buy, check these programs out. One of them is bound to fulfill your needs.

Comodo Cleaning Essentials

Available on Windows XP, Vista, and 7 for 32-bit and 64-bit systems.

As a company, Comodo has impressed me quite a bit in recent years. They have over 30 products that are useful for home use, e-commerce, small businesses, large enterprises, and social media. They cover fields from cloud backup to SSL certificates to Internet security to firewall and VPN programs. If it’s Internet-related, they probably have a product for it.

So you can imagine how unsurprised I was when I learned they had a computer cleaning toolkit. The program itself looks simple, clean, and does what it’s meant to do – scan your computer for virus and malware threats and quarantine them.

Suffice it to say that Comodo Cleaning Essentials is not the best scanner available, even in the free software market, but it’s quick and painless. It’ll detect the most serious of threats, but some of the more mundane ones will slip through on occasion.

Malwarebytes Anti-Malware Free

Available on Windows XP, Vista, and 7 for 32-bit and 64-bit systems.

Malwarebytes is one of the most popular anti-malware and threat detection programs at the time of writing this article. Every time I search for antivirus and anti-malware related topics, Malwarebytes comes up. I’ve been using it as my primary threat scanner for at least 4 years and I don’t see an end to it anytime soon.

The great thing about Malwarebytes is that the Quick Scan feature is the only scan you need. The Full Scan is, for all intents and purposes, a placebo. If you don’t believe me, founder and CEO of Malwarebytes, Marcin Kleczynski, had this to say in a recent Reddit AMA thread:

We’ve designed the quick scan to detect everything. The full scan is there for people who won’t believe us.

What does this mean for you? You can kiss Full Scans goodbye. No more 20-minute scans! They’ve designed their program to detect malicious threats on your computer all within a 2-3 minute timespan. Color me impressed.

ClamWin AntiVirus Portable

Available on Windows 2000, XP, Vista, 7, and 8 for 32-bit and 64-bit systems.

According to ClamWin’s statistics, it is being used by over 600,000 people every day. That should be enough proof that ClamWin is an effective antivirus and anti-malware tool. It comes in an easy-to-use installer, or you can use the portable version instead to take it with you on-the-go and use it anywhere. Plus, it’s open source.

Don’t be fooled by its simplistic interface. ClamWin may look outdated, but it packs a potent punch when it comes to finding and eradicating threats on your computer. Personally, I’ve never seen a free antivirus scanner that detects as much stuff as ClamWin does. In addition, ClamWin’s virus and malware databases are constantly being updated, so you’ll always be catching the latest threats.

One of the greatest aspects of ClamWin (which could also be a downside) is that you have to manually scan each file. Of course, you can scan entire directories if you want, but that means longer scan times as it analyzes each individual file. If you only want to scan certain files, though, ClamWin excels.

Spybot Search & Destroy Portable

Available on Windows 2000, XP, Vista, 7, and 8 for 32-bit and 64-bit systems.

I remember when the Internet was still younger (or at least younger than it currently is) and malware was just starting to wreak havoc. In those days, Spybot S&D was one of the pioneers of anti-malware strategy, and alongside Lavasoft’s Ad-Aware, Spybot S&D could always be found as a recommendation for virus and malware removal.

These days, Spybot S&D’s performance has fallen by the wayside a bit, being outshined by programs like Malwarebytes and ClamWin. Still, Spybot works well, in my opinion, and the latest version has detected a number of threats that were missed by some of my regular antivirus scanners.

My only regret with Spybot S&D is the lack of a Quick Scan feature. If you want to scan, you need to run a Full Scan, which took 20 minutes on my above-average computer rig.

Kaspersky Security Scan

Available on Windows XP, Vista, 7, and 8 for 32-bit and 64-bit systems.

Kaspersky Lab is one of the most well-known security developers and for good reason. They’ve created over a dozen security programs that can be used for personal use, family use, and business use. They’ve specialized in it for years, so you can have faith that they know what they’re doing.

Their program packages will all cost you money (as low as $9.95 up to $179.95) but they do offer a free online antivirus scan that will detect and diagnose potential virus and malware threats. The downside is that it only detects–it doesn’t fix or repair or remove the found threats. For that, you’ll have to purchase one of their programs.

Not the best deal in the world, but their scanning program is good and will catch a few things that other scanners might miss. It’s worth giving a shot.

Conclusion

Again, one-time-scan antivirus programs are meant to be used at your convenience. If you suspect a virus-related issue on your computer, you can boot up the scanner and focus your efforts then. It frees up a lot of resources when you aren’t scanning, reducing the slowdown of your computer.

But be aware that using a one-time-scanner places the responsibility of scanning on you. If you let a virus or malware threat reside for too long and you end up in a situation you don’t want to be in (e.g., spyware infection), then the fault is entirely your own. If you accept that responsibility, then the above scanners will suit you just fine.