It seems that not a day goes by without a new online threat rearing its ugly head. With confusing terms such as worms, Trojans and rootkits being bandied around, it’s tempting to just throw up your hands and admit defeat.

However, although there is a lot of jargon relating to online threats, once you understand the basics, protecting yourself is not nearly as confusing as it might first seem.

Software that attempts to gain unauthorised access to your PC or network is often known as malware (an amalgamation of the words ‘malicious’ and ‘software’). In this article, we’ ll take you through the most common threats, detailing what detectives would call their modus operandi – or MO for short – what they do and how they do it. We’ll also consider the motives behind the spread of each type of threat.

With a clear understanding of online security threats, you’ll also be able to better protect your private documents and financial details and enjoy the huge benefits of the online world with peace of mind.

Viruses

MO: Slip in unnoticed, cause damage then replicate
Motive: Vandalism and bragging rights

Often used as a term to describe all forms of malware, a computer virus is essentially a program that wants to harm your computer in one way or another. A virus will look to infect your PC, often cause some level of damage to it and will then attempt to spread itself to as many other computers as possible. A virus may simply display an irritating message on your screen, while others delete documents or even the entire contents of the hard disk.

Viruses are created by people. The code has to be written and tested to make sure it works before being released, usually as some kind of free download or as an email attachment so it can spread.

The motive for this kind of behaviour often has its roots in the same kind of thinking that gives some people pleasure from acts of vandalism. Some virus creators revel in the idea that they are capable of creating and distributing something that can cause havoc in technology created by big, rich companies.

Unlike some other forms of malware, viruses can’t spread on their own. Instead, they need help from computer users, who are often completely unaware of the presence of the virus. In the past, most viruses were spread by infected floppy disks or CDs being passed from one computer to another. These days, with most computers connected to the internet, it’s far more likely that you’ll be infected by virus via an email attachment or download.

If your anti-virus software doesn’t pick up an infection, it’s often very difficult to tell that your PC has been attacked by a virus. However, if the virus is particularly malicious you will often notice a sudden slowdown in the responsiveness of your PC, along with unusually high disk activity. You can view your PC’s mem ory and processor usage in the Task Manager.

We explain how to interpret the information provided by the Task Manager.

It goes without saying that the best form of protection from viruses is installing up-to-date anti-virus software, which scans incoming files from the internet and email for known viruses.

Many modern anti-virus software packages use a technique called heuristics to detect malware as it occurs by identifying unusual PC behaviour. You also need to make sure that you never open email attachments from unknown sources.

Rootkit

MO: Master of disguise
Motive: Opens the door for other malware

The biggest problem that viruses, worms and other forms of malware face is that of detection by security software on the host PC. Rootkits, however, are masters of disguise. By mimicking legitimate systems files, they manage to take full (or ‘root’) control of a PC. Once installed, a rootkit can then be used to allow viruses, worms and other malware to infect the PC without being detected.

Rootkits hit the headlines in 2005, when Sony BMG installed one on a large number of its audio CDs. This rootkit then installed itself on any PCs on which the CDs were played.

It wasn’t malicious in that it was never intended to cause harm; it was instead designed to facilitate Sony’s copyright protection software in an attempt to prevent unauthorised copying of the music.

However, once a rootkit is installed on a computer, other viruses can use it to stay undetected. Sony soon released a removal tool, but viruses that took advantage of the rootkit had already surfaced. Needless to say, it wasn’t Sony BMG’s finest hour.

Rootkits were initially very successful because the vast majority of security suites simply didn’t scan for them. Thankfully, it’s a different story these days, with most suites including specific rootkit detectors. However, it’s worth noting that although most paid-for security software include rootkit scanners, many free suites, such as AVG Free, do not.

All is not lost, though, and if you take a look at our Top 10 Downloads section at the end of this feature you will see a link to a free rootkit scanner and remover.