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Adware
Adware is software that generates advertisements, usually as banner ads or pop-up windows. Adware is usually bundled with other software and installed without your knowledge. While usually not physically damaging or outright malicious, the intrusive behavior of adware can be annoying and waste system resources.
Cache file
Cache files are used to store information on a temporary basis for quick access. A common example of a cache file is a browser cache. Every time you open a Web page, your browser creates a cache file (a temporary copy) of the page's text and graphics. When you open the page again, your browser checks the Web site server for changes. If the page hasn't changed, your browser loads the page from cache on your hard drive, which is much faster than originally loading it from the remote server.
Cookie
A cookie is a small text file that some Web sites save to your local, hard drive while you are browsing the site. Cookies contain identifying information, such as log in and shopping cart information. Cookies are useful for loading Web site preferences and login settings, but they can also contain information that can be passed to others without your knowledge, usually for advertising purposes.
Fragment/Defragment
Over time, as you create, delete, and download files, your computer cannot store data as one unit and instead will split it up and store pieces in various drive locations. A fragmented hard drive has a large amount of such scattered data and can significantly slow PC performance. Similar to hard drives and other storage media, system memory can also become fragmented with time and usage.
Defragmenting reorganizes data so that components are stored closer to each other. Regularly defragmenting hard drives and system memory improves drive speed, reclaims valuable memory, and extends the life of your computer.
Malware
Malware (MALicious softWARE) is a generic term covering a range of software programs that are designed to damage computers or to obtain unauthorized information from computers. Some specific types of malware include viruses, worms, and Trojans.
Registry
The registry is a database that holds configuration settings used by your Windows operating system. The registry is vital to your computer’s ability to run correctly. It stores key data that Windows requires and continually references, such as user profiles and settings for installed software and hardware.
Only manually edit the registry if you know what you are doing; making inaccurate modifications can severely damage your computer. Always back up the registry prior to making any changes.
Spyware
Spyware is tracking software that is installed on your computer without your notice or consent. It sends information about your computing activities back to its source, usually for advertising purposes, but sometimes for much more dangerous purposes such as identity theft or credit card fraud.
The effect of spyware varies depending on what its creator’s intentions are and can include consumption of valuable system resources, random lockups, crashes, or slowdowns; Web browser Home page or search page redirection; unwanted software installation; and random or incessant pop-up ads.
Trojan
A Trojan, or Trojan horse, is a software program that appears to be desirable or useful, but intentionally does something you do not expect. The effects of Trojans can range from simply displaying pop-up ads to destroying files or enabling the theft of data.
Trojans are distributed in executable files, such as through email attachments, CDs, and Internet downloads. People can be lured into installing a Trojan because it appears that it will serve a legitimate purpose. Unlike viruses and worms, a Trojan is not designed to make automatic copies of itself. However, Trojans can carry viruses and other malicious software within them.
Two specific types of Trojans are keyloggers and RATs:
* A keylogger, or keystroke logger, captures all keystrokes and then records that information to a log file. With a keylogger, a hacker can capture your logins, passwords, credit card numbers, and any other confidential information that you type. Once collected, this information can be silently transmitted to the Trojan’s creator for malicious purposes, such as credit card or bank fraud.
* A remote access Trojan (RAT) gives someone remote access to and control of a computer. With a RAT, imposters can send email messages that will appear to be from you; read, modify, or destroy your documents; and use your PC to attack and infect other computers.
Virus
A computer virus is a software program designed to alter the operation of a computer. Most viruses are malicious and intended to cause damage, but even a benign virus can harm a system. Viruses can damage files, software programs, the registry, and hardware.
Viruses are distributed in executable files, such as through email attachments, CDs, and Internet downloads. A virus infection occurs when the infected file is run. A virus also automatically replicates, or makes copies of itself, by secretly embedding its programming code into other programs.
The term virus is often used as a generic, collective reference that includes other types of malicious programs, such as worms and Trojans.
Worm
A computer worm is a software program designed to reproduce and spread among computers. Most worms are malicious and intended to overwhelm system memory or network bandwidth. Worms can crash an entire network of computers or an individual computer.
Worms are generally distributed in email attachments or through unprotected Internet activity. A worm spreads very rapidly because it is self-contained. It replicates itself and, unlike viruses, a worm does not need to infect another program to spread.