We have all been infested with malware and all have at least some Adware present on our computers at this very moment. There are a lot of programs available for download to clean these up and to increase the speed of our PCs, some are free and some cost money. Which ones are genuine and which ones not? I would never recommend those that do a scan for free and then charge to download the cleaner. These invariably give false positives when the scan is done telling you that you have umpteen viruses and worms and countless other nasties. These positives are part of the program with the intention to harass and frighten and to coerce you into paying for the cleaning download. Never trust them. Viruses. You canâ€™t clean a compromised system by using a virus scanner. To tell you the truth, a fully compromised system canâ€™t be trusted. Even virus scanners must at some level rely on the system to not lie to them. If they ask whether a particular file is present, the attacker may simply have a tool in place that lies about it, (rootkit). If you can guarantee that the only thing that compromised the system was a particular virus or worm and you know that this virus has no back doors associated with it, and the vulnerability used by the virus was not available remotely, then a virus scanner can be used to clean the system. For example, the vast majority of e-mail worms rely on a user opening an attachment. In this particular case, it is possible that the only infection on the system is the one that came from the attachment containing the worm. However, if the vulnerability used by the worm was available remotely without user action, then you canâ€™t guarantee that the worm was the only thing that used that vulnerability. It is entirely possible that something else used the same vulnerability. In this case, you canâ€™t just patch the system. Patches. For those using Windows, ensure that the automatic updates is enabled, or if you don't want that, then make sure you visit the Microsoft Update site Microsoft Updates often. Microsoft issues a vunerability remover every first Thursday of the month, use it before you get a problem. You canâ€™t clean a compromised system by using some â€œvulnerability remover.â€ Letâ€™s say you had a system hit by Blaster. A number of vendors published vulnerability removers for Blaster. Can you trust a system that had Blaster after the tool is run? I wouldnâ€™t. If the system was vulnerable to Blaster, it was also vulnerable to a number of other attacks. Can you guarantee that none of those have been run against it? I didnâ€™t think so. You canâ€™t clean a compromised system by patching it. Patching only removes the vulnerability. Upon getting into your system, the attacker probably ensured that there were several other ways to get back in. You canâ€™t clean a compromised system by removing the back doors. You can never guarantee that you found all the back doors the attacker put in. The fact that you canâ€™t find any more may only mean you donâ€™t know where to look, or that the system is so compromised that what you are seeing is not actually what is there. You canâ€™t clean a compromised system by reinstalling the operating system over the existing installation. Again, the attacker may very well have tools in place that tell the installer lies. If that happens, the installer may not actually remove the compromised files. In addition, the attacker may also have put back doors in non-operating system components. You canâ€™t trust the event logs on a compromised system. Upon gaining full access to a system, it is simple for an attacker to modify the event logs on that system to cover any tracks. If you rely on the event logs to tell you what has been done to your system, you may just be reading what the attacker wants you to read. The only guaranteed way to clean a compromised system is to flatten and rebuild. If you have a system that has been completely compromised, the only thing you can do is to flatten the system (reformat the system disk) and rebuild it from scratch (reinstall Windows and your applications). If you use your PC for Banking, Business, Important things and surfing, then you are vunerable. You should never use a Business PC for general surfing, buy another one for that. For the rest of us, just ensure you have taken precautions, (not condoms), and update what we have installed regularly. Who to trust. Only trust programs from recognised vendors and coders or as recommended by well known and recognised computer magazines. A few very trusted names for antivirus to remember are: Aladdin Knowledge Systems Alwil Software Authentium Inc Computer Associates International Inc Dr Web Ltd Eset FRISK Software International F-Secure CorpGFI Software Ltd Grisoft HAURI Inc Kaspersky Lab McAfee Inc Microsoft Corporation MicroWorld Technologies Inc Norman Panda Software Proland Software Sophos Sybari Software Inc Symantec Trend Micro Inc For malware. Internet Security - Kaspersky Lavasoft - Adaware Safer Networking - Spybot Search & Destroy. This list is not exhaustive. There is one thing to bear in mind if you are contemplating Symantec Norton. Norton contains 'Spyware' and Spybot search and destroy will pick this up. Symantec advise the removal of Spybot for this very reason and to hide the fact that Norton contains spyware. Do Not Remove Spybot, or at least install it again after installing Norton. Linux Linux has vunerablilities just like Windows, these may be different vunerabilities, but they are there all the same. The advantage at present with Linux is it's low take up, so it is not newsworthy or profitable to attack it. There are attacks frequently though so just be aware of that. It is becoming more popular and some big businesses are taking it up, especially for servers, so it will come under attack more often as it gains in popularity. .