Types of threats

A computer worm is a self-replicating computer program. It uses a computer network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. This is due to security shortcomings on the target computer. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer

Worms spread by exploiting vulnerabilities in operating systems. Vendors with security problems supply regular security updates, and if these are installed to a machine then the majority of worms are unable to spread to it. If a vendor acknowledges a vulnerability, but has yet to release a security update to patch it, a zero day exploit is possible. However, these are relatively rare.

Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. They are mostly intended for data-stealing

A Trojan horse is any program that invites the user to run it, concealing a harmful or malicious payload. The payload may take effect immediately and can lead to many undesirable effects, such as deleting the user's files or further installing malicious or undesirable software. Trojan horses known as droppers are used to start off a worm outbreak, by injecting the worm into users' local networks.

Trojan horses may allow a hacker remote access to a target computer system. Once a Trojan horse has been installed on a target computer system, a hacker may have access to the computer remotely and perform various operations, limited by user privileges on the target computer system and the design of the Trojan horse.

A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability. A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.




Spyware is a type of malware that is installed on computers and collects little bits of information at a time about users without their knowledge. The presence of spyware is typically hidden from the user, and can be difficult to detect. Typically, spyware is secretly installed on the user's personal computer. Sometimes, however, spywares such as keyloggers are installed by the owner of a shared, corporate, or public computer on purpose in order to secretly monitor other users.
While the term spyware suggests that software that secretly monitors the user's computing, the functions of spyware extend well beyond simple monitoring. Spyware programs can collect various types of personal information, such as Internet surfing habits and sites that have been visited, but can also interfere with user control of the computer in other ways, such as installing additional software and redirecting Web browser activity. Spyware is known to change computer settings, resulting in slow connection speeds, different home pages, and/or loss of Internet or functionality of other programs. In an attempt to increase the understanding of spyware, a more formal classification of its included software types is captured under the term privacy-invasive software.

@special nice information

WORM

A worm is a computer program that replicates and propagates to itself without having to attack itself to a host unlike a virus, which needs to attach itself to a computer program or host.A worm that replicates itself multiple times and can infect any computer(System) in very short period of time ,it is very difficult to detect.Sometimes worms are updated remotely.
common source for worms are LAN , e-mails etc.
Solution for worms: Update the system and anti-virus regularly, always use firewall(must ON).
The most famous worms are Code Red.

i have one question,
What vulnerability did the worm use to propagate itself?

TROJAN

Trojan programs are one of the most common and frequent programs which attack networks and PCs. It is also smarter programs which shows users that it is very useful and get installed by the users ,finally you installed a virus program not the necessary information.In this was user install a blackdoor or rootkit on his computer.
Backdoors or rootkit are computer program that give attackers a mean of regaining access to the attacked computer later.
A rootkit is created after an attack and usually hides itself within the computer tools(files so folders) and very difficult or almost impossible to detect.
Usually firewall would likely to identify traffic that's sing unfamiliar ports, but Trojan is much smarter that it uses common ports, like TCP Port 80(HTTP) or UDP Port 53(DNS), are more difficult to detect.
Common source are torrents,suspicious downloads,web sites
Solution:user must be very careful while downloading.

VIRUS

A virus is most common.It is a program that attacks to an executable file.It can replicate itself, usually through an executable file program and usually attached to an e-mails.Once it attacks to a program such as Microsoft Word, it performs whatever the creator(Who created virus program) designed it to do.
Common source: flash memory,LAN etc
Solution:use security tool.

SPYWARE

A spyware programs sends information from the infected computer to the person who initiated the spyware program on host computers.
These information are in the form of dialog box asking to enter the relevant information like confidential data,password, PINs and the spyware program get register each text entered. This type of technology used to record and send everything a user enters to an unknown person.

One more thing i want to add is ADWARE

Adware is almost same as spyware.The adwares main purpose is to determine a user's purchasing habits so that WEB browser can display advertisements.The adware generally slow downs the host computer.