Malware: Software out to get you
June 12th, 2010
What is Malware?
Malware is software designed to infiltrate or damage a computer system without the owner’s informed consent. It is a combination of the words malicious and software. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code.
Most computer users are not familiar with the term and don’t use it. Instead, “computer virus” is commonly used incorrectly to describe all kinds of malware, though not all malware are viruses.
What is a Computer Virus?
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. A virus can only spread from one computer to another when its “host” (the infected file) is taken to an uninfected computer. This can happen by a user sending it over a network, the Internet, or by carrying it on a removable medium such as a floppy disk, CD, or USB drive.
Today, viruses are somewhat less common than network-borne worms, due to the popularity of the Internet. Anti-virus software, originally designed to protect computers from viruses, has in turn expanded to cover worms and other threats such as spyware, identity theft and adware.
Ways in which viruses and worms spread:
- Web browsing security holes
- Instant Messaging
- File sharing systems (Peer-to-peer networks)
- USB drives
- Shared network drives
Types of Viruses
Trojan horses
A Trojan horse, or simply trojan, is a piece of software which appears to perform a certain action but in fact performs another such as a computer virus. Trojan horses are different from a virus because a trojan cannot replicate automatically.
Worms
A worm is a piece of software that uses computer networks and security flaws to create copies of itself. A copy of the worm will scan the network for any other machine that has a specific security flaw. It replicates itself to the new machine using the security flaw, and then begins scanning and replicating anew.
E-mail viruses
An e-mail virus will use an e-mail message as a mode of transport, and usually will copy itself by automatically mailing itself to hundreds of people in the victim’s address book.
Often, a malicious file like a Word document, PDF, image, video, batch file, etc. can be attached to the e-mail and the user is tricked into opening the file. There are software protections that will scan e-mail attachments for you. Additionally, it is a wise practice to not open video files and others in an e-mail attachment.
Logic Bombs
A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time or when some other condition is met. This technique can be used by a virus or worm to gain momentum and spread before being noticed. Many viruses attack their host systems on specific dates, such as Friday the 13th or April Fool’s Day. Malware that activates on certain dates are often called “time bombs”.
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