Basic Computer Viruses

Charles Bailey

computersafetyComputer viruses used to be something users only read about in science fiction novels. But today, users need to understand the techniques of software sabotage that can be destructive and untraceable when used with a virus program.

Four basic types of malicious software may be part of a computer virus:

* A trapdoor is a set of special instructions embedded in the operating system, enabling anyone who knows about it to bypass normal security procedures and gain access to computer files.

A trapdoor is set legitimately during creation of the operating system, usually for debugging purposes. Programmers who develop large applications and operating systems often insert debugging aids that provide breaks in the code for later insertion of new code.

Operating systems and applications should be designed to prevent accessing or changing the code.

However, during software development, built-in safeguards are bypassed for efficiency’s sake. Trapdoors usually are eliminated in the final stage of product development but can be overlooked intentionally or unintentionally.

* A logic bomb is a computer program or part of a program executed at a certain time to facilitate an unauthorized or malicious act. The most common type is the time bomb, set to go off at a specific future time after the perpetrator has left the organization.

For example, a logic bomb might check the system date every day until it encounters the date it is programmed to go off. At that time it carries out its mission.

* A worm program is similar to an Autoexec file because it runs every time the system is booted up. Worms originally were developed by systems programmers who needed extra memory to run large programs and wanted to tap unused resources on a network.

The worm program searches the computer and network for idle machines, using them to execute the large program in small segments.

Underlying worm maintenance mechanisms are responsible for maintaining the worm, finding free machines when needed and replicating the program for each additional segment.

* In a Trojan horse attack, new instructions or logic are added to a computer program or circuit before it is used. During processing, the unauthorized, changed or new functions are performed along with normal activity. The Trojan horse is the most common method of program-based fraud and sabotage.

Instructions may be placed in production programs so they will execute in the protected or restricted domain of the program, with access to all the data files assigned for exclusive use of the program. Most programs are constructed loosely enough for space to be found or created to insert these instructions.

Rivera, Angel L. “Computer viruses can infect entire organizations.” Government Computer News 29 Apr. 1988: 37.

So how does one protect against this kind of stuff these days anyway?  There are thankfully a plethora of different software programs that can help to prevent and also remove malware and viruses.  Some, such as Spyhunter 4, work to actively protect the user’s computer.  Others, such as SpeedyPC Pro (check out this Speedy PC Pro review) work to remove the malware after the attack.  Of course it’s a good idea to prevent malware in the first place, and so we highly recommend Spyhunter 4 type programs with active protection.