Viruses, Trojans and Worms
What are computer viruses, Trojans and worms?
Simply stated, a virus, Trojan or worm is a small program written to cause harm to one or more computers or networks. A Virus, Worm or Trojan can also be designed to retrieve information from your computer to be delivered to an attacker for future use. For example, credit card information, passwords, and security access codes.
More specifically, a virus is a parasitic program designed to enter a person's computer clandestinely. The virus attaches itself to files or boot sectors and is self-replicating.
A Trojan (or Trojan horse) is a malicious program that pretends to be a benign application. It is designed to cause your computer to do something that is unexpected. Since it does not spread (not self-replicating) it is not really a virus.
A worm is a parasitic program designed to replicate itself on your computer and then spread to other computers via email (through your address book or contact list).
What types of files are most likely to be infected?
Programs of the following types are the most likely to be infected with a virus. New viruses are developed daily, so this list is not, nor can it be all-inclusive.
CERT: Recovering from Viruses, Worms, and Trojan Horses
CERT: Coordinating Virus and Spyware Defense
CERT: Understanding Hidden Threats: Corrupted Software Files
CERT: Understanding Hidden Threats: Rootkits and Botnets
CSCIC: Viruses/Spyware (Video)
MS-ISAC: What You need to Know About Botnets!
Simply stated, a virus, Trojan or worm is a small program written to cause harm to one or more computers or networks. A Virus, Worm or Trojan can also be designed to retrieve information from your computer to be delivered to an attacker for future use. For example, credit card information, passwords, and security access codes.
More specifically, a virus is a parasitic program designed to enter a person's computer clandestinely. The virus attaches itself to files or boot sectors and is self-replicating.
A Trojan (or Trojan horse) is a malicious program that pretends to be a benign application. It is designed to cause your computer to do something that is unexpected. Since it does not spread (not self-replicating) it is not really a virus.
A worm is a parasitic program designed to replicate itself on your computer and then spread to other computers via email (through your address book or contact list).
What types of files are most likely to be infected?
Programs of the following types are the most likely to be infected with a virus. New viruses are developed daily, so this list is not, nor can it be all-inclusive.
- exe
- com
- vbs
- mp3
- drv
- sys
- bin
- script files
- macros
- Only download or accept files from reliable sources.
- Use a firewall to block unauthorized access to your computer.
- Install a good anti-virus program and keep it updated
- Scan all e-mail attachments and downloaded files before opening
CERT: Recovering from Viruses, Worms, and Trojan Horses
CERT: Coordinating Virus and Spyware Defense
CERT: Understanding Hidden Threats: Corrupted Software Files
CERT: Understanding Hidden Threats: Rootkits and Botnets
CSCIC: Viruses/Spyware (Video)
MS-ISAC: What You need to Know About Botnets!
