Different Types of Malware and How They Work

Malware is a collective term used to represent virus, worms, spyware and other malicious programs out there on the Internet. In simple words, any software program that is intended to cause direct or indirect harm to the computer system is referred to as a malware.

Some malware programs cause serious problems such as destroying the system files, causing disruption to the computer operation or gathering sensitive information while others may only have a light impact such as redirecting websites to pornographic content or annoying the users with pop-ups and banners.

In the normal routine, we have often seen every malicious program being referred to as a virus, but this is not correct! In fact, as mentioned earlier, there exists several malicious programs where virus is one among them. Now, many of you may may be wondering to know what’s the difference between them. Well, this article gives a detailed information on different types of malware that exist, how they work and how they differ from each other:

1. Computer Virus:

As we all know, this is the type of malware that has become highly popular and is one of the most widely discussed topic in the field of computer security. A virus is just a computer program that is designed to take unauthorized control of the infected computer so as to cause harm to the system’s data or degrade it’s performance.

Mode of operation:

Computer viruses operates by attaching themselves to an already existing file or program and replicates itself to spread from one computer to another. In most cases, they tend to infect executable files that are parts of legitimate programs. So, whenever the infected file is executed on a new computer, the virus gets activated and begins to operate by further replication or causing the intended damage to the system.

A virus cannot perform it’s task of harming and replication unless it is allowed to execute. This is the reason why viruses often choose an executable file as it’s host and get attached to them. Viruses are mainly classified into two types:

Non-Resident Viruses: 

This kind of virus will execute along with it’s host, perform the needful action of finding and infecting         the other possible files and eventually transfers the control back to the main program (host). The operation of the virus will terminate along with that of it’s host.

Resident Viruses:
In case of resident viruses, whenever the infected program is run by the user, the virus gets activated, loads it’s replication module into the memory and then transfers the control back to the main program. In this case, the virus still remains active in the memory waiting for an opportunity to find and infect other files even after the main program (host) has been terminated.

Damages caused:

Viruses are known to cause destruction of data and software programs. In some cases, a virus may do nothing other than just replicating itself. However, they are responsible for using a large portion of the system resources such as CPU and memory which results in the performance degradation of the computer.

2. Trojan horse:

A Trojan horse or simply called as Trojan is a type of malicious program that disguises itself as something that is legitimate or useful. The main purpose of a trojan is to gain the trust of the user from the front end, so that it gets the permission to be installed. But, from the back end, it is designed to grant unauthorized control of the computer to the hacker.

Mode of operation:

A Trojan horse do not depend on the host to carry out it’s operation. So, unlike a computer virus it does not tend to attach itself to other files. Trojans are often disguised as video codecs, software cracks, keygens and other similar programs downloaded from untrusted sources. So, one has to be careful about those untrusted websites that offer free downloads.

One of the most popular example is the DNSChanger trojan that was designed to hijack the DNS servers of the victimized computers. It was distributed by some of the rogue pornographic websites as a video codec needed to view online content.

Damages caused:

Trojan horses are known to cause a wide variety of damages such as stealing passwords and login details, electronic money theft, logging keystrokes, modify/delete files, monitor user activity etc.

3. Worms:

Worms are standalone computer programs with a malicious intent that spread from one computer to another. Unlike viruses, worms have the ability to operate independently and hence do not attach themselves to another program.

Mode of operation:

Worms often use a computer network to spread itself by exploiting the security vulnerabilities that exist inside the individual computers. In most cases, worms are designed only to spread without causing any serious change to the computer system.

Damage caused:

Unlike viruses, worms do not cause damage to the system files and other important programs. However, they are responsible for consuming the bandwidth thereby degrading the performance of the network.

4. Spyware:

Spyware is a type of malicious software that can collect information about the activities of the target computer without the knowledge of it’s users. Spywares such as keyloggers are often installed by the owner or administrator of the computer in order to monitor the activities of the users. This can be a parent trying to monitor his child, a company owner trying to monitor his employee or someone trying to spy on his/her spouse.

Mode of operation:

Spywares are designed to operate in a totally stealth mode so that it’s presence is completely hidden from the users of the computer. Once installed, they silently monitor all the activities on the computer such as keystrokes, web activity, IM logs etc. These logs are stored secretly for later access or uploaded online so that the installer of the spyware program can have access to them.

Damage caused:

Apart from monitoring, spywares do not cause any damage to the computer. However, in some cases the affected computer may experience degradation in it’s performance.

5. Adware:

Adware is a software program that automatically renders advertisements to the users without their consent. Most common examples are pop-ups, pop-unders and other annoying banner ads. The prime reason behind the design of adware is to generate revenue for it’s author.

Mode of operation:

Adwares are are often bundled up with some of the free utilities such as a browser toolbars, video downloaders etc. When such programs are installed, the adware may take over and distract user activity by displaying annoying advertisements.

Damage caused:

Adware is harmless in most of the occasions. However, some are known to contain spywares that are used to monitor the surfing habits of users. This may pose a threat to the privacy of the users.