Security threats are everywhere: in downloads, peer-to-peer networks, hidden in the data on CDs or DVDs, embedded in emails and their attachments, spread through chat rooms and messengers. Once malware gets to your PC, it will reduce system performance, modify and destabilize your system, and hog your Internet bandwidth.
Here are the 5 ways how malware do this.
The popular belief is that malware or malicious software either destroys your data by wiping your hard drive clean, or compromises it by stealing your information and sending it to third parties, which is not entirely true.
These are common effects but some malware just affect system performance hogging resources and drastically slowing your PC down.
1. Malware Degrades System Performance
Malware degrades system performance usually when it infects files with .exe, .scr, .ocx extensions and spreads through a variety of methods. The virus resides in memory and usually will infect files again after removal, because of great resilience. The malware adds data to files making them larger and larger. This causes system instability, poor system performance, and unusual behaviour of the PC.
Example of malware: W/32 Funlove
2. Malware Makes System Unstable
Some malware like worm W32/Blaster takes advantage of a vulnerability in Windows (2000, XP, NT and Server 2003) and causes unexpected system error messages and automatic reboots. There are several variants of this worm, but most of them have the same Modus Operandi. Effects include registry modification and unusual behaviour. Registry modification is particularly dangerous as it may effect the overall operation of your PC, even causing an inability to start Windows.
Example of malware: W32/Blaster variations
3. Malware Generates Unusual System Behaviour
Unusual behaviour means that your PC doesn’t act like it used to behave. You may notice change in settings, logs, even access to certain applications. Other effects include DoS (Denial of Service) attacks and modification of the System registry and may even grant remote access to your computer. Malware usually spreads itself through email and over the file-sharing networks.
Example of malware: W32/Mydoom (recorded as "the worst e-mail worm incident in virus history" by F-Secure in 2004)
4. Malware Modifies the System Registry
Almost every malicious software messes with the System registry, because that’s the way how malware protects itself (by shutting down vital processes that can help in malware removal). By modifying the registry, malware hides itself from the user. One of the most difficult malware to detect is W32/Lovgate worm. It spreads through email and over network shares, while trying to open up remote connections to computers through backdoors. This malware for example opens up port 10168, which is the software addresses used by applications running on one computer to communicate with other applications that run on other systems across a network. By knowing the Internet address of the victim's computer, the port number and the password used by the Trojan horse, an intruder can take control of an infected PC.
Example of malware: W32/Lovgate
5. Malware Downloads Code from the Internet
Another worm that spreads through email is W32/Sobig. This worm has its own SMTP engine that allows it to send emails and to propagate itself on other machines. Once activated, the worm downloads a list of web addresses to which it then connects to download a code or program and subsequently run it on the infected machine. In a Local Network environment, this malware will also try to copy itself onto shared folders.
Example of malware: W32/Sobig
There are plenty of new worms and viruses that have been created each day in order to replace those who are already discovered and restrained. Keep in mind that you must have activated ‘The Holy Trinity’ of the PC security: Antivirus, Firewall and Antispyware/Antitrojan software. Also, keep your whole system up to date in order to keep the malware out of your system.