Introduction to Information Security

Computer Systems Security

Malicious software and protections against it

DEFINITION

• Malicious software is a software that is intentionally included or inserted in a system for a harmful purpose.
• Malicious software, also known as “malware,” is a nuisance, but increasingly, malicious software can damage data, computers, and computer networks. Examples include Trojan horses, vandalware, spyware, hoaxes, some viruses—including macro viruses—and worms.

MALICIOUS SOFTWARE

Malicious Programs

Backdoor or Trapdoor

• It is a secret entry point into a program.
• It also allows those who know to access bypassing usual security procedures.
• It have been commonly used by developers.
• Backdoors become threats when unscrupulous programmers use them to gain unauthorized access.
• It is difficult to implement operating system controls for backdoors.
• It requires good s/w development & update.

Logic Bomb

• It is one of oldest types of malicious software.
• The logic bomb is code embedded in legitimate program.
• It is activated when specified conditions met.

E.g. presence/absence of some file

particular date/time

particular user

• When triggered typically damage system , modify/delete files/disks, halt machine, etc.

Trojan Horse

• It is a program or command procedure with hidden side-effects .
• Trojan horse program can be used to accomplish functions indirectly .

E.g. game, s/w upgrade etc.

• It allows attacker to indirectly gain access that they do not have directly.
• It is often used to propagate a virus/worm or install a backdoor or simply to destroy data.
• Another common motivation for the Trojan horse is data destruction. The program appears to be performing a useful function (e.g., a calculator program), but it may also be quietly deleting the user’s files.