Top Free Online Virus Scan Services

Free online virus scan is a very popular service among all PC users worldwide. The reasons are obvious - always up-to-date antivirus signature databases, ease of use, simple interface which even novice users find comfortable to work with (because all it takes to run a scanner is a couple of mouse clicks), quite wide choice of scanners at no cost.

Nowadays all big name antivirus companies offer some kind of online scan for present and future customers. It is also part of marketing strategy exploited to attract buyers. Whenever a free online virus scan finds and removes some infection, it is natural to suggest that a paid installation of antivirus would do real miracles to data safety and protection. A very effective on-going advertising campaign, isn't it? ;)

Anyway, it would be foolish not to use the option of online virus scan if such can help when your PC security is questioned.

Online scanners have quite significant advantages over dekstop installations of traditional antivirus software and PC security suites, to name just a few: 

• Always free to use! No demo versions, no trials, no registration keys to enter.
• Online virus scanner cannot be corrupted by infections hiding somewhere inside Windows files, while it does happen to on-disk installations of PC security software. Some sophisticated malware can easily damage antivirus software installed under Windows and make it absolutely useless. I've seen this happened to different products.
• There's a choice of services, so you can always decide what you want specifically to be done in every case. Online scan services offer removal of rootkits, spyware and other threats in addition to virus infections. But you can't really install several antivirus applications under Windows simultaneously (some people suggest that you use 2 antivirus softwares installed side-by-side, but you may run into trouble like conflicting resident scanners 'fighting' in memory to kick each other out of RAM space).
• Sometimes you can't install an antivirus because the already infected Windows corrupts the setup process. This is when you either go for a CD-bootable anti-virus, or load a browser and initiate an online virus scan.
• If you dislike some particular online virus scanner, there's no need to go through a removal process like installed programs require. Downloaded antivirus signatures are kept as temporary files, so they're easily removed from the hard drive via settings of a browser. There are no changes made to the sensitive Windows registry (arguably the most vulnerable part of Windows).

With all that said, I can't leave the negative points beyond. There are some:

• Online scanners cannot perform when there's no stable Internet connection. If a virus messes up the TCP/IP configuration, chances are you will not be able to use online scan service.
• A browser will require certain privileges on part of the user for the online scan to perform. If privileges are limited and there are no sufficient rights under user account to download signature files, etc, online antivirus will be unusable. So user accounts with restricted rights may experience a problem.
• Smart virus can prevent online scan from running.
• Online virus scan is a one-time solution, it cannot prevent future infections. 
• Not all online virus scan service offers removal of the detected malware - some only report the found infections.

• Because most online virus scanners depend on Internet Explorer and ActiveX, it may be necessary to repeat the scan after restarting computer, and/or switching to another scanner. This is because malware often corrupts IE system files and injects malicious code into IE settings, so it is not always possible for the scanner to remove all detected threats at once. Some malicious entries are left, but the dependence of alien files is broken, so the next time you load up the scanner, it procedes with the removal process and cleans out the PC.

Below I'm listing most popular (in my opinion) services offering free online virus scan.

Trend Micro HouseCall offers a free online virus and spyware scan. This is the service you'll most likely see recommended in first place on many PC security related forums. It is indeed that popular! TrendMicro scan goes far beyond bare virus detection, supports Windows and Mac based computers, Mozilla and Internet Explorer browsers. Important: you can choose from either ActiveX engine or Java engine. These set of options make this online scan very versatile. Currently there's a new version available for testing ;)

Go to Trend Micro Housecall.

BitDefender appeals to my aesthetics - I like its interface. It works in two modes - simple and advanced, depending on how much information you want displayed. The progress bar is very convenient. It shows the number of scanned files, infections, and actions taken. Besides, BitDefender allows send a report to their security lab once the scan is finished and there is a virus detected, thus you can help this great product become even better ;) The drawback is that it supports IE browser only. For a Firefox fan like me it's not that convenient. But it is indeed a powerful service, which I've seen detect infections other products failed to.

Another great feature of BitDefender is the ability to choose directories for scanning. Say, if you have several HDD partitions, you can limit scanning to C:\Windows and My Documents, where malware is most likely to be living. This option can significantly reduce the time compared to the full computer scan.

Go to BitDefender Online Scan.

McAfee FreeScan is the name! I guess it is the synonym for computer security in the US ;) Like a narrative. The scanning service is solid as everything produced by the brand. As to cons, it requires IE 5.0+ and works with ActiveX controls only. If ActiveX is disabled, than you can't use the service.

McAfee FreeScan offers a browser window with real-time statistics - number of files scanned, infections, name of detected virus.

Go to McAfee FreeScan.

F-Secure offers to scan a PC for common infections like virus and rootkits. It also removes the found infections. However, F-Secure needs Internet Explorer to run, and doesn't have support for Firefox as of yet. But fans of Internet Explorer 7 may happily use this service ;)

Windows Vista is supported in addition to previous Windows versions.

Go to F-Secure Online Virus Scan.

ESET's Online Antivirus Scanner uses its patented ThreatSense technology which is featured in company's desktop and server products. Initial download of antivirus signature database takes under a minute if you're on a broadband. ESET offers to remove the detected infections - for this you need to check the proper boxes (see screenshots below). Spyware is removed as well! NOD32 Scanner works only with ActiveX so it requires Internet Explorer (as most online virus scan services do).

Go to ESET Online Antivirus Scanner.

Kaspersky claims its Online Scanner to have the highest detection rate. To some extent, it is true. What's amazing is that online scan has even higher detection rate than Kaspersky Antivirus itself! Its antivirus database is updated hourly which may be considered to be the fastest response to emerging online threats.

Kaspersky online virus scanner uses two platforms to run: Internet Explorer with Microsoft ActiveX technology, and Mozilla FireFox with Java. This is a big step forward since now we, surfers, have more flexibility.

A big con of Kaspersky online virus scan is that it doesn't have a removal option, that is all detected infections are for your consideration only. I think that Kaspersky is a good scanner to verify that your PC is 100% clean, but inability to remove the malware certainly doesn't allow to call it perfect.

In addition to online scanner, Kaspersky offers to check individual files for possible infections. Handy if you're not sure about certain file (like screensaver).

Downloading signature database requires at least several minutes, so be prepared to wait a bit before the online scanner will be ready to run.

Kaspersky scanner offers 2 types of scan: standard and advanced. The former detects virus infections, trojans, worms, and rootkits, while the latter adds up spyware, adware and the like. Obviously the second scan type takes more time to complete.

Additionally you have the option to let the service scan files inside archives (rar, zip, etc) and email attachments.

Note: because Kaspersky Online Scan service doesn't allow neither removal nor healing of detected infections, my suggestion is that you use some other scanner to eliminate present malware. However, I myself use Kasperksy to verify the clean state of the system. Two scans are always better than one, don't you agree? ;) And Kaspersky is important because it is the only PC security scanner developed by Russian programmers, so its algorithms are very much unique.

Go to Kaspersky Online Scanner.

Panda security vendor offers anyone to try out its TruPrevent technology. With a database of 185,000 threats its online scan can not only detect, but also remove the infections. Additionally scans for spyware modules (like dialers, jokes, rootkits, etc).

Panda claims to be able to desinfect the known spyware, and thanks to its heuristic engine, it detects even unknown types of malware.

The antivius database is updated every day.

Optionally you can place a shortuct on your desktop to connect to Panda ActiveScan whenever you need to, without opening a browser window.

Note: if you have antivirus software installed with resident monitoring ON, it may report a virus in Panda downloadable files. Do not worry! This is a common false-positive. The reason is that Panda doesn't encrypt its database of antivirus definitions, and when it is being downloaded onto your PC, a stand-alone AV can decide you're getting infected. Other security vendors set some kind of encryption to its malware definitions so that no third party AV software is able to detect the virus signatures inside archives. Rest assured that Panda is not infecting your PC.

Go to Panda ActiveScan.

Ewido used to be a pretty powerful PC security software developer, with its Ewido antispyware being still recommended forhome users.

Attention: smart computer owners can enjoy this little known trick to have a nice Ewido anti-spyware with latest updates. Though Ewido antispyware is no longer supported (because AVG Group purchased it), you still can get the installer. You can't purchase a serial key to make it PRO, so Ewido will be working as on-demand scanner only. However, it is a very good application, even not considering the price ;)

The latest version of Ewido Antispyware ever released was 4.0.0.172

Download: Ewido Anti-spyware (Rapidshare mirror)

I uploaded it to Rapidshare for everyone willing to have additional antispyware security layer.

AVG acquired Ewido because of its strong scanning engine. Since that, AVG improved its own algorithms greatly.

However, Ewido still offers a web version of its scanner, which is available to all Internet Explorer users.

Go to: Ewido Online Scan

Apart from listed above virus scans, there sometimes rises a need to check the safety of one single file. To do it quickly, it is best to use a corresponding service for scanning separate files - without the need to download anti virus definitions.

Among such services the following are worth mentioning.

Avast! Online Scanner.

There's a captcha to be entered in order to scan a file. All you need to do is just browse for the target file on your PC, enter the captcha and press 'Scan' button.

Go to Avast! Online Virus Scanner.

DrWeb Online Scan.

DrWeb is another PC security product from Russia. The desktop version of DrWeb is very popular in Russia and CIS countries - and there must be serious reasons for that. DrWeb offers to scan single files - the webpage is as simple as possible, there's nothing on it except the "browse" button to specify the path to the target file.

Go to DrWeb Web Scanner.

VirusTotal.

VirusTotal deserves special attention. It provides interface in multiple languages. It's anti virus definitions database in compiled by biggest PC security software developers - that is, a single scan equals to simultaneous scanning with different antivirus engines.

Virus Total receiced a PC World Magazine Award in 2007 as one of 100 best products of the year.

The cool thing about this service is that it allows to send files for scan via Email and even place a context command! That way you can send a file for thorough scan just by right-clicking mouse.

Go to VirusTotal Scanning Service.

Ewido, now a part of AVG Group, though ceased to support its anti-spyware desktop product, still offers a nice online virus scan.

Ewido workd on IE + ActiveX platform only. It has very simple interface, and no newbie will happen to get lost there. When you visit the page, Ewido informs you that an ActiveX control needs to be loaded - accept it since it's absolutely safe. When ActiveX component installation completes, Ewido starts downloadig its latest definitions (see below).

Configuring settings for running Ewido online virus scanner is a no sweat task: there's nothing to configure at all. You don't have to get through a dozen of malware types to specify which you want detected and which not. Just look through the list of all available drives in your system and uncheck those you don't want scanned, then click the single button below to start virus scan.

I decided to scan a D: drive and found out that Ewido scans a newly installed Windows XP with SP3 pretty fast. Sure it found nothing, but I would be surprised if it had. Ewido's online scan can be aborted at any time, and started anew. As soon as you click the "Scan" button, there appear two more below to give you the options.

Because Ewido was known for a very effective anti-spyware program, which now is branded by AVG Anti-spyware (part of AVG Internet Security Suite 8.0), I expect it's online scanner to have a greater focus on spyware threats, which is great because powerful anti-spyware scanners are in great demand right now.

Go to: Ewido Online Virus Scan.

Windows Live OneCare is available both in a desktop version and an online virus scanner. The latter allows to check hard drive for unnecessary files and delete them, and also tests the strength of PC security setup.

As you can guess for sure Microsoft requires Internet Explorer to be used for running Windows Live OneCare scanner.

Go to: Windows Live OneCare Safety Scanner.

It's been a couple of months since EMSISOFT updated it's desktop a-squared anti-malware to version 4.0, and now the company decided to join the army of online virus scanners!

a-squared web malware scanner offers anyone to check computers for Trojan Viruses, Worms, Backdoors, Rootkits, Spyware/Adware, Keyloggers, Dialers, Hacking Tools, Riskware and TrackingCookies. All you need to run this tool is Internet Explorer with ActiveX enabled and a stable Internet connection.

a-squared online scanner requirements:

• Windows XP or Windows Vista;
• Internet Explorer 5.0+
• User account with administrator privileges;
• 32-bit system .

Upon first scan you will be prompted to install a-squared ActiveX components. Agree to that.

Just like the desktop version of a-squared anti-malware, the web scanner will offer to choose from 4 types of scan:

• Quick scan;
• Smart scan;
• Deep scan;
• Custom scan.

Quick scan is meant for fast checking of Windows most sensitive areas, like Windows and System32 folders, Documents and Settings, system memory, and the Registry.

Smart scan also checks Program Files for malicious software installers.

Deep scan takes the longest to complete because it is a thorough check of all hard drive space, byte-by-byte to ensure not a single piece of malware is hiding in the system.

Custom scan allows you to choose which specific folders to check for malware presence.

The web malware scanner window conveniently displays the number of definitions loaded, and the date when latest updates were added to the database.

EMSISOFT offers a new a-squared free malware removal tool with web interface.

Go to: a-squared web malware scanner. 

When the scan is finished and if suspicious or malicious objects are detected, a-squared will offer to quarantine them. Then you can switch to the Quarantine mode and delete all of the unwanted objects. I just checked the scanner myself and can attest that it works smooth and causes no errors whatsoever. a-squared really makes great & free malware removal tools.