Anti-virus
You probably already that the purpose of an anti-virus program (aka virus scanner) is to detect and remove viruses (and other malware). The best known of all the essential things you need to have to keep your system secure, anti-virus software has been installed on all computers since the mid to late 90’s.
Viruses, Trojans, Worms…
You may have heard a variety of terms applied to malicious software: virus, trojan, worm, spyware, adware, macro virus, email virus…. The list could go on. All of these terms have specific meanings, but for the most part it is irrelevant to the end-user in regards to anti-virus software. They all do bad things.
There are two notable terms in there that are slightly different than the others though. A Trojan Horse is a program that pretends to be be one thing but in reality is doing something bad. For instance, you might run what looks like a simple game and meanwhile, in the background where you can’t see it, it is doing some sort of damage to your system. The other term is spyware. Spyware is technically just a program (often bundled with some other program you download) that collects personal data and then sends it to someone else. This can be as benign as ad preferences (i.e. you tend to click on ads about movies) or as bad as any credit card numbers, SSN’s, or passwords it can get it’s hands on. Often times as well adware (think popups not due to going to a new website) will get bundled in underneath the term spyware.
How this all relates to virus scanners is this: All anti-virus software will detect and remove (if possible) virus, worms, trojans and the like. Depending on just what software you use, it may or may not scan for spyware.
Why Always Using Anti-virus Software is Important
Viruses are probably the most prevalent threat to a user’s security. There are many viruses in the wild (alive and infecting computers on the internet) that an unprotected computer could easily become infected with. Many of these viruses can be avoided to a certain extent, but some will quickly infect computers that have not been properly updated as soon as they connect to the internet. Other types will come in through email, downloads, and even from websites you visit. Furthermore, if you don’t have a virus scanner, you may not even know that you’ve been infected. You computer may run slower, crash, or exhibit other strange behaviors, but you won’t be able to fix the problem if you don’t know it’s even there.
Anti-Spyware Software
Spyware, adware, etc can also do nasty things. As mentioned above, these types of programs can steal sensitive data and annoy you with popups. Some will even re-write search results from whatever search engine you use. They’ll insert their own ads and re-position searched items to further support their ads. I have seen many computers that are infected with so many of these types of programs that the computer becomes essentially unusable as it slows to a crawl while the spyware or adware do their things and spawn popups faster than you can close them.
Some virus-scanners (or at least the “security suite” package that they come in) will scan for spyware, but some won’t. Using a separate scanner is a must in the latter case and still desirable in the former as some spyware-scanners pick up some things better than others.
It is good to note that, just like firewalls, you can only have one anti-virus program installed at a time. Spyware scanners, on the other hand, generally don’t integrate themselves with windows like virus-scanners do and therefore you can have more than one installed.
Updating
Updating is an important part of good security in general, but with virus scanners it is absolutely critical. When anti-virus software updates, it gains the ability to find the latest viruses. You don’t want to get caught with an infection from the newest virus going around when an update was released days before hand. Fortunately, virtually (if not) all virus scanners automatically check for updates and then install them automatically. They are often set up to check every 24 hours or less so you’ll always have the most up to date protection. Most programs will let you manually configure whether or not you want it to check for updates for you, but generally they are configured to do this by default, so you shouldn’t have to worry about it.