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Programmed attacks exploit user vulnerabilities (weak passwords), introduce malicious code, and/or exploit service flaws in computing systems.

Denial of service, destruction of data, modification of data, and interception of data can all occur as a result of a programmed attack.

Viruses
Trapdoors
Trojan Horses
Salami Attacks
Worms
Greedy Programs

Viruses

A virus is an infectious program which affects computer systems and data. Viruses are spread to any other programs they contact, thus being infectious. A virus will attach a copy of itself to an executable program.

Viruses usually consist of a reproduction mechanism, a trigger mechanism, and an action.

Both malicious and benign viruses exist. Benign viruses are used for maintenance and for compression.

Introduced by executing a program (viruses are hidden in programs), be aware of all software you run on your systems. Safe practice dictates not downloading software from bulletin boards or from untrusted sources. By limiting the sharing of information the spread of viruses is limited.

Anti-Virus Resource Center

Trap Doors

Trap Doors are secret entry points to a program put in during development by the programmer. They may be used for testing or maintenance, but can also be used to gain unauthorized access at a later time.

Danger exists if the trap door is exploited by the original programmer or if it is discovered by others.

Trojan Horses

A trojan horse is a program with hidden functionality. An example is a program which captures passwords secretly. Trojan horses can occur by being buried in object code or by modifying existing source code.

Trojan horses may be encrypted or scattered throughout a program, making it difficult to detect.

Salami Attacks

A salami attack is a programmed attack which is implemented in small (meant to be unnoticeable) increments. Because it is occurring in small increments it is easily concealed.

Rounding down interest calculations and placing the difference in your account is an example of a salami attack.

Worms

A worm is a program which replicates itself over a network. Unlike a virus a worm does not need to attach itself to another program in order to replicate.

The Internet Worm released by Robert Morris is an example of the danger of worms and the magnitude of denial of service caused by a worm.

Greedy Programs

By using a significant portion of the CPU and other system resources, greedy programs result in a denial of service. Greedy programs can be accidental or malicious.

An example of a malicious greedy program is a mail bomb.