Computer Viruses and Malware Types

Polymorphic, companion, and FAT viruses are all recognized types of computer viruses. 'Memory virus' is not a standard classification in virology or computer science. While viruses do reside in memory, this is not considered a distinct virus category.

Resident viruses dwell permanently in RAM (Random Access Memory) after the initial infection, allowing them to remain active and infect other files. Hard disk and boot sector are storage locations where viruses can reside but are not where resident viruses specifically 'dwell' during active operation.

Polymorphic viruses constantly change their code (encrypt and decrypt) while keeping the functionality intact, making them impossible to detect using fixed string or signature searches. Each infection looks different to signature-based antivirus. Resident, Boot sector, and Macro viruses can be detected with signature-based methods.

FAT (File Allocation Table) viruses specifically target and damage the FAT sections of the hard disk, which the operating system uses to locate and access files. Boot Sector Viruses (B) infect the boot sector, while Hard Disk Virus (D) is not a standard classification. Crypto Viruses (A) encrypt files rather than damaging access sections.

Polymorphic viruses use various encryption algorithms and constantly change their encryption keys with each infection to evade detection by antivirus software. Companion Viruses (A) don't use encryption, Overwrite Viruses (C) simply overwrite file content, and File Infectors (D) attach to executable files without polymorphic encryption.

Worms (A) and Direct Action Viruses (C) both possess self-replication capabilities. Worms replicate independently across networks, while Direct Action Viruses replicate when specific files are executed. Trojan Horses (B) cannot self-replicate as they disguise themselves as legitimate software, and Polymorphic Viruses (D), while capable of replication, are not primarily defined by this property.

Trojan Horses and Logic Bombs are non-replicating malware - they require execution and don't self-copy. Overwrite Viruses replicate by infecting files, Worms self-replicate across networks. Only B and D lack self-replication capability, making them the correct MC-2 answer.

Trojan Horses are malicious programs that disguise themselves as legitimate software while creating backdoors for network intruders to access system information. Unlike worms which self-replicate, or macro viruses that infect documents, Trojans specifically focus on unauthorized access and data theft. Direct Action Viruses are a different category that infect files when executed.

Companion viruses exhibit characteristics of both Resident Viruses (which install in memory and infect files) and Direct Action Viruses (which infect files when executed and then remain dormant). They don't have properties of boot sector viruses, overwrite viruses, or directory viruses as their primary characteristics.

The ILOVEYOU virus (May 2000) caused estimated $10-15 billion in damages globally, infecting millions of computers via email with the subject 'ILOVEYOU'. Melissa (1999) was damaging but less widespread. Code Red (2001) targeted servers, and Chernobyl/CIH (1998) was destructive but not as economically damaging.

Antivirus software primarily uses two scanning methods: (1) Virus Signature Search - comparing files against known malware signatures, and (2) Behavioral Heuristic Analysis - detecting suspicious behavior patterns. 'Behavioral Search' is vague, and 'Pattern Search' is redundant with signatures. This covers the two main approaches.

Antivirus software primarily uses two methods: virus signature search (matching known malware patterns against a database) and behavioral heuristic algorithms (detecting suspicious activities by monitoring program behavior). Signature detection catches known threats, while heuristic analysis identifies potential new malware based on anomalous behavior patterns.

A virus hoax is a false warning about a non-existent computer virus that spreads through email chains, causing unnecessary panic. Unlike real viruses, hoaxes are purely social attacks that rely on human fear and credulity to propagate. Spoofing involves faking identities, hacking is unauthorized access, and spam refers to unsolicited bulk messages.