Tens
of thousands of virus/malware exist, with more being created each
day. Although once most common in DOS or Windows, computer viruses
today can cause a great amount of damage by exploiting vulnerabilities
in corporate networks, email systems and websites.
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Rootkit: A program (or collection of programs) that installs and executes code on a system without end user consent or knowledge. It uses stealth to maintain a persistent and undetectable presence on the machine. Rootkits do not infect machines, but rather, seek to provide an undetectable environment for malicious code to execute. Rootkits are installed on systems via social engineering, upon execution of malware, or simply by browsing a malicious website. Once installed, an attacker can perform virtually any function on the system to include remote access, eavesdropping, as well as hide processes, files, registry keys and communication channels.
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Trojan horse: This type of threat often uses ports to gain access to computers or executable programs. Trojan horse programs do not replicate but instead reside on systems to perform malicious acts, such as opening ports for hackers to enter. Traditional antivirus solutions can detect and remove viruses but not Trojans, especially those already running on the system.
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Virus: A program that replicates. To do so, the virus needs to attach itself to other program files and execute whenever the host program executes, including:
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Others: Virus/Malware not categorized under any of the other virus/malware types.