Hacker
Hacker is a computer and networking guru who tries to break into computer systems legelly or illegally.

Hacking
Hacking refers to the activities of programming and network intrusions.

Hacktivism
Hacktivism is the act of hacking, or breaking into a computer system, for a politically or socially motivated purpose. The individual who performs an act of hacktivism is said to be a hacktivist.

Hacktivist
A hacktivist uses the same tools and techniques as a hacker, but does so in order to disrupt services and bring attention to a political or social cause. For example, one might leave a highly visible message on the home page of a Web site that gets a lot of traffic or which embodies a point-of-view that is being opposed. Or one might launch a denial-of-service attack to disrupt traffic to a particular site.

Half-Open Scanning
Half-open scanning, also known as SYN scanning, is used by a malicious hacker (or cracker) to determine the state of a communications port without establishing a full connection. It could be used to perform denial-of-service (DOS) attacks.

Hardening
Hardening is the process of identifying and fixing vulnerabilities on a system by implementing the latest software paches, hotfixes and updates, using the latest and secured versions of protocols and following procedures and policies to reduce attacks and system down time.

Harrison-Ruzzo-Ullman Model
Harrison-Ruzzo-Ullman Model is a security model that provides policies for changing access rights and rights for the creation and deletion of subjects and objects. It is generally considered to be one of the more complex security models.

Hash
Hash is a mathematical algorithm that takes a variable-size message and returns a fixed-size string to authenticate (prove the integrity) of a message. Examples are SHA and M5, a component of IKE, IPsec and digital signatures.

Hash Function
Hash Function is a function associated with a table, that computes hash code. All hash functions have one argument, a key, and return two values, a hash id and a hash state, which together represent the hash code. See also equivalence predicate.

Hashing
Hashing is the transformation of a string of characters into a usually shorter fixed-length value or key that represents the original string. Hashing is used to index and retrieve items in a database because it is faster to find the item using the shorter hashed key than to find it using the original value. It is also used in many encryption algorithms.

Hashing algorithm
Hashing algorithm refers to a mathematical procedure that generates a fixed-size result from arbitrary amounts of data.

Heuristics
Heuristics is the application of experience-derived knowledge to a problem and is sometimes used to describe software that screens and filters out messages likely to contain a computer virus or other undesirable contents. A heuristic is a "rule-of-thumb."

Hex encoding URL attack
Hex encoding URL attack is a form of file system traversal attack using hexadecimal characters.

HFNetChk
HFNetChk is a Microsoft tool for keeping security patches up to date on a system.

Hidden file
Hidden files are not displayed by default when browsing the file system from the command line. Hidden files are generally important files relating to a user’s environment and are a target for exploits by hackers. On UNIX/Linux platforms, hidden files are files whose names begin with a period (“.”), and they are therefore often called dot files. Examples of hidden files commonly found in home directories include .login, .mailrc, and .forward. Once an attacker has compromised a system, attackers may create hidden directories with unusual names such as “.....” to hide utilities they may install such as backdoors and Trojans. The "find" command can be used to search for hidden files on a UNIX system.

HIDS: Host-Based IDS
Host-based intrusion detection systems (HIDS) use information from the operating system audit records to watch all operations occurring on the host that the intrusion detection software has been installed upon. These operations are then compared with a pre-defined security policy.

Hierarchy of trust
Hierarchy of trust, also known as certificate authority (CA) hierarchy, is the hierarchical collection of CAs bound together by trust relationships.

Hijack Attack
Hijack Attack is a form of active wiretapping in which the attacker seizes control of a previously established communication association/session. In addition to listening to the conversations, the hacker may change the messages to both parties, which results the Man-in-the-Middle attack.

Hijacking
Hijacking is a type of network security attack in which the attacker takes control of a communication between two entities and masquerades as one of them. The man in the middle attack is one type of hijacking where the perpetrator takes control of an established connection while it is in progress.

Hijackware
Hijackware, also known as browser hijacker, is a type of malware program that alters your computer's browser settings so that you are redirected to Web sites that you had no intention of visiting. Most browser hijackers alter default home pages and search pages to those of their customers, who pay for that service because of the traffic it generates.

HIPAA: Health Insurance Portability & Accountability Act
The Health Insurance Portability & Accountability Act (HIPAA) refers to the US Public Law 104-191. It is also known as the Kennedy-Kassebaum Act. HIPAA is designed to protect the confidentiality of patient records, past, present and future.

HMAC: Keyed-Hash Message Authentication Code
A keyed-hash message authentication code, or HMAC, is a type of message authentication code (MAC) calculated using a cryptographic hash function in combination with a secret key. As with any MAC, it may be used to simultaneously verify both the data integrity and the authenticity of a message. Any iterative cryptographic hash function, such as MD5 or SHA-1, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed as HMAC-MD5 or HMAC-SHA-1 accordingly.

HMAC-MD5: Hashed Message Authentication Codes with MD5
Hashed Message Authentication Codes with MD5 (HMAC-MD5) is a keyed version of MD5 that enables two parties to validate transmitted information using a shared secret.

Hoax Virus
A hoax virus, also known as hoax, is a false warning about a computer virus. Typically, the warning arrives in an e-mail note or is distributed through a note in a company's internal network. These notes are usually forwarded using distribution lists and they will typically suggest that the recipient forward the note to other distribution lists.

Homeland Security Act
The Homeland Security Act was signed by President Bush on November 25, 2002. Like the Patriot Act, it was enacted in response to the terrorist attack of 9/11, 2001.

Honey Pot or Honeypot
Honey pots, also known as honeypots, are software programs that simulate one or more network services that you designate on your computer's ports. Honey pot can also be an Internet-attached server that acts as a decoy, luring in potential hackers in order to study their activities and monitor how they are able to break into a system. Honeypots are designed to mimic systems that an intruder would like to break into but limit the intruder from having access to an entire network. A honey pot can be used to log access attempts to those ports including the attacker's keystrokes.

Honeynet
A honeynet is a network set up with intentional vulnerabilities to invite attack, so that an attacker's activities and methods can be studied and that information be used to increase network security. A honeynet contains one or more honey pots, which are computer systems on the Internet expressly set up to attract and "trap" people who attempt to penetrate other people's computer systems

Honeynet Project
The Honeynet Project is a non-profit volunteer organization dedicated to computer security research and information sharing. The group developed the first operational honeynet (a network set up with intentional vulnerabilities for the purpose of attracting attackers) and actively promotes the deployment of further honeynets.

HOPE: Hackers On Planet Earth
Hackers On Planet Earth (HOPE) is a popular series of conferences for black hat hackers.

Host-based security
Host-based security refers to the security implemented by configuring each host on a network.

Hops
A hop is each exchange with a gateway a packet takes on its way to the destination.

Host-Based IDS
Host-based intrusion detection systems (IDS) use information from the operating system audit records to watch all operations occurring on the host that the intrusion detection software has been installed upon. These operations are then compared with a pre-defined security policy.

Hot Site
A hot site is a commercial disaster recovery service that allows a business to continue computer and network operations in the event of a computer or equipment disaster. For example, if an enterprise's data processing center becomes inoperable, that enterprise can move all data processing operations to a hot site.

Hot Site and Cold Site
Hot site and cold site both provide disaster recovery services. A hot site is a commercial disaster recovery service that allows a business to continue computer and network operations in the event of a computer or equipment disaster. A cold site provides disaster recovery services such as office space, but the customer provides and installs all the equipment needed to continue operations. A cold site is less expensive, but it takes longer to get an enterprise in full operation after the disaster.

Hotfixes
Hotfix, created by vendors to address compatibility or functional problems, is the patch component designed to repair problems occuring on a relatively small number of computers.

Hping
Hping, also known as Hping2, is a security tool for testing and auditing Transmission Control Protocol/Internet Protocol (TCP/IP) networks.

Hping2
Hping2, also known as Hping, is a packet generation and crafting tool, which can be used by attackers to compromize, crash, or fool network equipment.

HSM: Hardware security module
Hardware security module (HSM) is a hardware device used for protecting cryptographic keys.

htaccess
htaccess is a configuration file for Apache Web servers. Information such as access usernames and passwords to a specific folder can be set up using the htaccess file.

HTTP Attack
HTTP Attack uses HTTP port (port 80) or HTTP communications to perform attacks. Since http is the primary protocol used for web communication, web attacks are often asociated with HTTP attacks.

HTTP over SSL
Secure Socket Layer (SSL) is an open, nonproprietary protocol that Netscape has proposed as a standard to the World Wide Consortium (W3C). HTTP can run on top of TLS or SSL for secured transactions, which is called HTTPS. HTTPS is not to be confused with S-HTTP, a security-enhanced version of HTTP developed and proposed as a standard by IETF.

HTTP Proxy
A HTTP Proxy is a server that acts as a middleman in the communication between HTTP clients and web servers.

HTTPS: Hypertext Transfer Protocol Secure
Hypertext Transfer Protocol Secure (HTTPS) refers to the HTTP running on top of TLS or SSL for secured transactions. HTTPS is not to be confused with S-HTTP, a security-enhanced version of HTTP developed and proposed as a standard by IETF.

Hybrid Attack
A Hybrid Attack builds on the dictionary attack method by adding numerals and symbols to dictionary words.

Hybrid Encryption
Hybrid Encryption is an application of cryptography that combines two or more encryption algorithms, particularly a combination of symmetric and asymmetric encryption.

Hybrid Virus
A hybrid virus (sometimes called a multi-part or multipartite virus) is one that combines characteristics of more than one type to infect both program files and system sectors. The virus may attack at either level and proceed to infect the other once it has established itself. Hybrid viruses can be very difficult to eradicate and, unless completely eradicated, will often reinfect the host system repeatedly.

Hyper Hasher
Hyper Hasher is a shareware program authored by Matt "Cyber Dog" LaPlante. The goal of Hyper Hasher is to allow the user to compute digital file hashes and checksums in more formats than any other program. It also allows for fast comparison of multiple files in any supported format.

Hyperlink
In hypertext or hypermedia, an information object (such as a word, a phrase, or an image; usually highlighted by color or underscoring) that points or link to related information that is located on other web pages and can be retrieved by activating the link.

Hyperlink Spoofing
Hyperlink spoofing, also called as web spoofing, is a means by which an attacker is able to see and make changes to web pages that are transmitted to or from another computer. These pages may include confidential information such as credit card number entered online. This technique is used in data phishing.