World Library  
Flag as Inappropriate
Email this Article

Computer insecurity


Computer insecurity

This article is about computer security exploits and defenses. For computer security through design and engineering, see computer security.

Computer insecurity is the concept that a computer system is always vulnerable to attack, and that this fact creates a constant battle between those looking to improve security and those looking to circumvent security.

Security and systems design

Although there are many aspects to take into consideration when designing a computer system, security can prove to be very important. According to Symantec, in 2010 94 percent of organizations polled expect to implement security improvements to their computer systems, with 42 percent claiming cyber security as their top risk.[1]
At the same time many organizations are improving security, many types of cyber criminals are finding ways to continue their activities. Almost every type of cyber attack is on the rise. In 2009 respondents to the CSI Computer Crime and Security Survey admitted that malware infections, denial-of-service attacks, password sniffing, and web site defacements were significantly higher than in the previous two years.[2]

Financial cost

Serious financial damage has been caused by security breaches, but because there is no standard model for estimating the cost of an incident, the only data available is that which is made public by the organizations involved. “Several computer security consulting firms produce estimates of total worldwide losses attributable to virus and worm attacks and to hostile digital acts in general. The 2003 loss estimates by these firms range from $13 billion (worms and viruses only) to $226 billion (for all forms of covert attacks). The reliability of these estimates is often challenged; the underlying methodology is basically anecdotal.”[3] Insecurities in operating systems have led to a massive black market for rogue software. An attacker can use a security hole to install software that tricks the user into buying a product. At that point, an affiliate program pays the affiliate responsible for generating that installation about $30. The software is sold for between $50 and $75 per license.[4]


There are many similarities (yet many fundamental differences) between computer and physical security. Just like real-world security, the motivations for breaches of computer security vary between attackers, sometimes called hackers or crackers. Some are thrill-seekers or vandals (the kind often responsible for defacing web sites); similarly, some web site defacements are done to make political statements. However, some attackers are highly skilled and motivated with the goal of compromising computers for financial gain or espionage. An example of the latter is Markus Hess (more diligent than skilled), who spied for the KGB and was ultimately caught because of the efforts of Clifford Stoll, who wrote a memoir, The Cuckoo's Egg, about his experiences. For those seeking to prevent security breaches, the first step is usually to attempt to identify what might motivate an attack on the system, how much the continued operation and information security of the system are worth, and who might be motivated to breach it. The precautions required for a home personal computer are very different for those of banks' Internet banking systems, and different again for a classified military network. Other computer security writers suggest that, since an attacker using a network need know nothing about you or what you have on your computer, attacker motivation is inherently impossible to determine beyond guessing. If true, blocking all possible attacks is the only plausible action to take.


To understand the techniques for securing a computer system, it is important to first understand the various types of "attacks" that can be made against it. These threats can typically be classified into one of these seven categories:


An exploit (from the same word in the French language, meaning "achievement", or "accomplishment") is a piece of software, a chunk of data, or sequence of commands that take advantage of a software "bug" or "glitch" in order to cause unintended or unanticipated behavior to occur on computer software, hardware, or something electronic (usually computerized). This frequently includes such things as gaining control of a computer system or allowing privilege escalation or a denial of service attack. Many development methodologies rely on testing to ensure the quality of any code released; this process often fails to discover unusual potential exploits. The term "exploit" generally refers to small programs designed to take advantage of a software flaw that has been discovered, either remote or local. The code from the exploit program is frequently reused in trojan horses and computer viruses. In some cases, a vulnerability can lie in certain programs' processing of a specific file type, such as a non-executable media file. Some security web sites maintain lists of currently known unpatched vulnerabilities found in common programs (see "External links" below).


Eavesdropping is the act of surreptitiously listening to a private conversation, typically between hosts on a network. For instance, programs such as Carnivore and NarusInsight have been used by the FBI and NSA to eavesdrop on the systems of internet service providers. Even machines that operate as a closed system (i.e., with no contact to the outside world) can be eavesdropped upon via monitoring the faint electro-magnetic transmissions generated by the hardware such as TEMPEST.

Social engineering and human error

A computer system is no more secure than the human systems responsible for its operation. Malicious individuals have regularly penetrated well-designed, secure computer systems by taking advantage of the carelessness of trusted individuals, or by deliberately deceiving them, for example sending messages that they are the system administrator and asking for passwords. This deception is known as Social engineering.

Denial-of-service attack

Unlike other exploits, denial of service attacks are not used to gain unauthorized access or control of a system. They are instead designed to render it unusable. Attackers can deny service to individual victims, such as by deliberately entering a wrong password 3 consecutive times and thus causing the victim account to be locked, or they may overload the capabilities of a machine or network and block all users at once. These types of attack are, in practice, very hard to prevent, because the behavior of whole networks needs to be analyzed, not only the behaviour of small pieces of code. Distributed denial of service (DDoS) attacks are common, where a large number of compromised hosts (commonly referred to as "zombie computers", used as part of a botnet with, for example; a worm, trojan horse, or backdoor exploit to control them.) are used to flood a target system with network requests, thus attempting to render it unusable through resource exhaustion. Another technique to exhaust victim resources is through the use of an attack amplifier — where the attacker takes advantage of poorly designed protocols on 3rd party machines, such as FTP or DNS, in order to instruct these hosts to launch the flood. There are also commonly found vulnerabilities in applications that cannot be used to take control over a computer, but merely make the target application malfunction or crash. This is known as a denial-of-service exploit.

Indirect attacks

An indirect attack is an attack launched by a third party computer. By using someone else's computer to launch an attack, it becomes far more difficult to track down the actual attacker. There have also been cases where attackers took advantage of public anonymizing systems, such as the tor onion router system.


A backdoor in a computer system (or cryptosystem or algorithm) is a method of bypassing normal authentication, securing remote access to a computer, obtaining access to plaintext, and so on, while attempting to remain undetected. The backdoor may take the form of an installed program (e.g., Back Orifice), or could be a modification to an existing program or hardware device. A specific form of backdoors are rootkits, which replaces system binaries and/or hooks into the function calls of the operating system to hide the presence of other programs, users, services and open ports. It may also fake information about disk and memory usage.

Direct access attacks

Someone who has gained access to a computer can install any type of devices to compromise security, including operating system modifications, software worms, key loggers, and covert listening devices. The attacker can also easily download large quantities of data onto backup media, for instance CD-R/DVD-R, tape; or portable devices such as keydrives, digital cameras or digital audio players. Another common technique is to boot an operating system contained on a CD-ROM or other bootable media and read the data from the harddrive(s) this way. The only way to defeat this is to encrypt the storage media and store the key separate from the system.

See also: Category:Cryptographic attacks

Reducing vulnerabilities

Computer code is regarded by some as a form of mathematics. It is theoretically possible to prove the correctness of certain classes of computer programs, though the feasibility of actually achieving this in large-scale practical systems is regarded as small by some with practical experience in the industry — see Bruce Schneier et al.

It's also possible to protect messages in transit (i.e., communications) by means of cryptography. One method of encryption — the one-time pad — is unbreakable when correctly used. This method was used by the Soviet Union during the Cold War, though flaws in their implementation allowed some cryptanalysis (See Venona Project). The method uses a matching pair of key-codes, securely distributed, which are used once-and-only-once to encode and decode a single message. For transmitted computer encryption this method is difficult to use properly (securely), and highly inconvenient as well. Other methods of encryption, while breakable in theory, are often virtually impossible to directly break by any means publicly known today. Breaking them requires some non-cryptographic input, such as a stolen key, stolen plaintext (at either end of the transmission), or some other extra cryptanalytic information.

Social engineering and direct computer access (physical) attacks can only be prevented by non-computer means, which can be difficult to enforce, relative to the sensitivity of the information. Even in a highly disciplined environment, such as in military organizations, social engineering attacks can still be difficult to foresee and prevent.

In practice, only a small fraction of computer program code is mathematically proven, or even goes through comprehensive information technology audits or inexpensive but extremely valuable computer security audits, so it's usually possible for a determined hacker to read, copy, alter or destroy data in well secured computers, albeit at the cost of great time and resources. Few attackers would audit applications for vulnerabilities just to attack a single specific system. It is possible to reduce an attacker's chances by keeping systems up to date, using a security scanner or/and hiring competent people responsible for security. The effects of data loss/damage can be reduced by careful backing up and insurance.

Security measures

A state of computer "security" is the conceptual ideal, attained by the use of the three processes:

  1. Prevention
  2. Detection
  3. Response
  • User account access controls and cryptography can protect systems files and data, respectively.
  • Firewalls are by far the most common prevention systems from a network security perspective as they can (if properly configured) shield access to internal network services, and block certain kinds of attacks through packet filtering.
  • Intrusion Detection Systems (IDSs) are designed to detect network attacks in progress and assist in post-attack forensics, while audit trails and logs serve a similar function for individual systems.
  • "Response" is necessarily defined by the assessed security requirements of an individual system and may cover the range from simple upgrade of protections to notification of legal authorities, counter-attacks, and the like. In some special cases, a complete destruction of the compromised system is favored, as it may happen that not all the compromised resources are detected.

Today, computer security comprises mainly "preventive" measures, like firewalls or an Exit Procedure. A firewall can be defined as a way of filtering network data between a host or a network and another network, such as the Internet, and can be implemented as software running on the machine, hooking into the network stack (or, in the case of most UNIX-based operating systems such as Linux, built into the operating system kernel) to provide realtime filtering and blocking. Another implementation is a so-called physical firewall which consists of a separate machine filtering network traffic. Firewalls are common amongst machines that are permanently connected to the Internet. However, relatively few organisations maintain computer systems with effective detection systems, and fewer still have organised response mechanisms in place. As result, as Reuters points out: “Companies for the first time report they are losing more through electronic theft of data than physical stealing of assets”.[5] The primary obstacle to effective eradication of cyber crime could be traced to excessive reliance on firewalls and other automated “detection” systems. Yet it is basic evidence gathering by using Packet Capture Appliances that puts criminals behind bars.

Difficulty with response

Responding forcefully to attempted security breaches (in the manner that one would for attempted physical security breaches) is often very difficult for a variety of reasons:

  • Identifying attackers is difficult, as they are often in a different jurisdiction to the systems they attempt to breach, and operate through proxies, temporary anonymous dial-up accounts, wireless connections, and other anonymising procedures which make backtracing difficult and are often located in yet another jurisdiction. If they successfully breach security, they are often able to delete logs to cover their tracks.
  • The sheer number of attempted attacks is so large that organisations cannot spend time pursuing each attacker (a typical home user with a permanent (e.g., cable modem) connection will be attacked at least several times per day, so more attractive targets could be presumed to see many more). Note however, that most of the sheer bulk of these attacks are made by automated vulnerability scanners and computer worms.
  • Law enforcement officers are often unfamiliar with information technology, and so lack the skills and interest in pursuing attackers. There are also budgetary constraints. It has been argued that the high cost of technology, such as DNA testing, and improved forensics mean less money for other kinds of law enforcement, so the overall rate of criminals not getting dealt with goes up as the cost of the technology increases. In addition, the identification of attackers across a network may require logs from various points in the network and in many countries, the release of these records to law enforcement (with the exception of being voluntarily surrendered by a network administrator or a system administrator) requires a search warrant and, depending on the circumstances, the legal proceedings required can be drawn out to the point where the records are either regularly destroyed, or the information is no longer relevant.

See also

Lists and categories

Individual articles

Notes and references

Further reading

  • Ross J. Anderson: Security Engineering: A Guide to Building Dependable Distributed Systems, ISBN 0-471-38922-6
  • Bruce Schneier: Secrets & Lies: Digital Security in a Networked World, ISBN 0-471-25311-1
  • Cyrus Peikari, Anton Chuvakin: Security Warrior, ISBN 0-596-00545-8
  • Jack Koziol, David Litchfield: The Shellcoder's Handbook: Discovering and Exploiting Security Holes, ISBN 0-7645-4468-3
  • Clifford Stoll: The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage, an informal — and easily approachable by the non-specialist — account of a real incident (and pattern) of computer insecurity, ISBN 0-7434-1146-3
  • ACSAC 1996
  • William Caelli: 2002
  • story of a community network that was cracked and what was done to recover from it 2000
  • Shon Harris, "CISSP All-In-One Study Guide" ISBN 0-07-149787-0
  • Daniel Ventre, "Information Warfare" Wiley - ISTE - 2009 - ISBN 978-1-84821-094-3
  • Daniel Ventre, "La guerre de l'information" - Hermès ISTE - 2007 - 300 pages
  • Daniel Ventre, "Cyberguerre et guerre de l'information. Stratégies, règles, enjeux" - Hermès Lavoisier - 2010
  • Daniel Ventre, "Cyberespace et acteurs du cyberconflit" - Hermès Lavoisier - avril 2011 - 288 pages
  • Daniel Ventre, "Cyberwar and Information Warfare" - Wiley ISTE - July 2011 - 460 pages
  • Daniel Ventre, "Cyberattaque et Cyberdéfense" - Hermès Lavoisier - August 2011 - 336 pages
  • What is Spyware
  • November 5, 2012

External links

  • GNU Free Documentation License.
  • Article "Ross Anderson
  • The Information Security Glossary
  • The SANS Top 20 Internet Security Vulnerabilities
  • Amit Singh: A Taste of Computer Security 2004
  • USA Today

Lists of currently known unpatched vulnerabilities

  • Secunia
  • Bugtraq mailing list.
  • List of vulnerabilities maintained by the government of the USA
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.