Computer Viruses
• Definition: A computer virus is a malicious program designed to spread from one computer to another,
infecting and potentially damaging systems, files, and software.
• Functionality: Viruses attach themselves to legitimate programs or files, replicating when these
programs are executed, often leading to corrupted files, reduced performance, or loss of data.
• Types of Viruses:
o File Infector Viruses: Attach to executable files and activate when the infected file is run.
o Macro Viruses: Embed in documents and are activated when the document is opened.
o Boot Sector Viruses: Infect the master boot record of a storage device and are loaded when
the system boots.
o Polymorphic Viruses: Change their code to evade detection by antivirus software.
o Resident Viruses: Hide in a computer's memory, making it challenging to remove.
• Examples: ILOVEYOU, My doom, and Michelangelo.
2. Logic Bombs
• Definition: Logic bombs are malicious code hidden within a program that activates when specific
conditions are met, such as a particular date or an event.
• Functionality: Unlike viruses, logic bombs do not replicate. Instead, they remain dormant until
triggered. Once activated, they can cause data loss, file corruption, or other destructive actions.
• Usage: Often used by disgruntled employees as a form of sabotage or by hackers to gain control over
systems at a specified time.
• Examples: The “Friday the 13th” virus, which activates on a certain date.
3. Trojan Horses
• Definition: A Trojan horse is a type of malware disguised as legitimate software, tricking users into
installing it, which then allows unauthorized access to the system.
• Functionality: Once installed, Trojans can steal information, spy on users, delete files, or even allow
attackers to control the system remotely.
• Types of Trojans:
o Remote Access Trojans (RATs): Enable attackers to control the infected device remotely.
o Banking Trojans: Target financial information to steal bank account details.
o Downloader Trojans: Download and install other types of malware on the system.
o Fake AV Trojans: Pretend to be antivirus software but actually harm the system.
• Examples: Zeus, Emoted, and Spy Eye.
4. Worms
• Definition: Worms are self-replicating malware that spread independently across networks without
attaching to host programs.
• Functionality: Worms exploit network vulnerabilities, often causing network slowdowns or crashes
due to the massive amount of replication and spreading. Unlike viruses, worms do not require user
interaction to propagate.
• Impact: They can consume bandwidth, lead to data breaches, and cause financial and operational
losses for organizations.
• Definition: A computer virus is a malicious program designed to spread from one computer to another,
infecting and potentially damaging systems, files, and software.
• Functionality: Viruses attach themselves to legitimate programs or files, replicating when these
programs are executed, often leading to corrupted files, reduced performance, or loss of data.
• Types of Viruses:
o File Infector Viruses: Attach to executable files and activate when the infected file is run.
o Macro Viruses: Embed in documents and are activated when the document is opened.
o Boot Sector Viruses: Infect the master boot record of a storage device and are loaded when
the system boots.
o Polymorphic Viruses: Change their code to evade detection by antivirus software.
o Resident Viruses: Hide in a computer's memory, making it challenging to remove.
• Examples: ILOVEYOU, My doom, and Michelangelo.
2. Logic Bombs
• Definition: Logic bombs are malicious code hidden within a program that activates when specific
conditions are met, such as a particular date or an event.
• Functionality: Unlike viruses, logic bombs do not replicate. Instead, they remain dormant until
triggered. Once activated, they can cause data loss, file corruption, or other destructive actions.
• Usage: Often used by disgruntled employees as a form of sabotage or by hackers to gain control over
systems at a specified time.
• Examples: The “Friday the 13th” virus, which activates on a certain date.
3. Trojan Horses
• Definition: A Trojan horse is a type of malware disguised as legitimate software, tricking users into
installing it, which then allows unauthorized access to the system.
• Functionality: Once installed, Trojans can steal information, spy on users, delete files, or even allow
attackers to control the system remotely.
• Types of Trojans:
o Remote Access Trojans (RATs): Enable attackers to control the infected device remotely.
o Banking Trojans: Target financial information to steal bank account details.
o Downloader Trojans: Download and install other types of malware on the system.
o Fake AV Trojans: Pretend to be antivirus software but actually harm the system.
• Examples: Zeus, Emoted, and Spy Eye.
4. Worms
• Definition: Worms are self-replicating malware that spread independently across networks without
attaching to host programs.
• Functionality: Worms exploit network vulnerabilities, often causing network slowdowns or crashes
due to the massive amount of replication and spreading. Unlike viruses, worms do not require user
interaction to propagate.
• Impact: They can consume bandwidth, lead to data breaches, and cause financial and operational
losses for organizations.
