In the field of computer security, phishing is the criminally fraudulent process of attempting to acquire sensitive information such as usernames, passwords and credit card details by masquerading as a trustworthy entity in an electronic communication. Communications purporting to be from popular social web sites, auction sites, online payment processors or IT administrators are commonly used to lure the unsuspecting public. Phishing is typically carried out by e-mail or instant messaging, and it often directs users to enter details at a fake website whose look and feel are almost identical to the legitimate one. Even when using server authentication, it may require tremendous skill to detect that the website is fake. Phishing is an example of social engineering techniques used to fool users, and exploits the poor usability of current web security technologies. Attempts to deal with the growing number of reported phishing incidents include legislation, user training, public awareness, and technical security measures.
A phishing technique was described in detail in 1987, and the first recorded use of the term "phishing" was made in 1996. The term is a variant of fishing, probably influenced by phreaking, and alludes to baits used to "catch" financial information and passwords.
Link manipulation
Most methods of phishing use some form of technical deception designed to make a link in an e-mail (and the spoofed website it leads to) appear to belong to the spoofed organization. Misspelled URLs or the use of subdomains are common tricks used by phishers. In the following example URL, http://www.yourbank.example.com/, it appears as though the URL will take you to the example section of the yourbank website; actually this URL points to the "yourbank" (i.e. phishing) section of the example website. Another common trick is to make the anchor text for a link appear to be valid, when the link actually goes to the phishers' site. The following example link, http://en.wikipedia.org/wiki/Genuine, appears to take you to an article entitled "Genuine"; clicking on it will in fact take you to the article entitled "Deception". In the lower left hand corner of most browsers you can preview and verify where the link is going to take you.
An old method of spoofing used links containing the '@' symbol, originally intended as a way to include a username and password (contrary to the standard). For example, the link http://www.google.com@members.tripod.com/ might deceive a casual observer into believing that it will open a page on www.google.com, whereas it actually directs the browser to a page on members.tripod.com, using a username of www.google.com: the page opens normally, regardless of the username supplied. Such URLs were disabled in Internet Explorer, while Mozilla Firefox and Opera present a warning message and give the option of continuing to the site or cancelling.
A further problem with URLs has been found in the handling of Internationalized domain names (IDN) in web browsers, that might allow visually identical web addresses to lead to different, possibly malicious, websites. Despite the publicity surrounding the flaw, known as IDN spoofing or homograph attack, phishers have taken advantage of a similar risk, using open URL redirectors on the websites of trusted organizations to disguise malicious URLs with a trusted domain. Even digital certificates do not solve this problem because it is quite possible for a phisher to purchase a valid certificate and subsequently change content to spoof a genuine website.
Filter evasion
Phishers have used images instead of text to make it harder for anti-phishing filters to detect text commonly used in phishing e-mails.
Website forgery
Once a victim visits the phishing website the deception is not over. Some phishing scams use JavaScript commands in order to alter the address bar. This is done either by placing a picture of a legitimate URL over the address bar, or by closing the original address bar and opening a new one with the legitimate URL.
An attacker can even use flaws in a trusted website's own scripts against the victim. These types of attacks (known as cross-site scripting) are particularly problematic, because they direct the user to sign in at their bank or service's own web page, where everything from the web address to the security certificates appears correct. In reality, the link to the website is crafted to carry out the attack, making it very difficult to spot without specialist knowledge. Just such a flaw was used in 2006 against PayPal.
A Universal Man-in-the-middle Phishing Kit, discovered by RSA Security, provides a simple-to-use interface that allows a phisher to convincingly reproduce websites and capture log-in details entered at the fake site.
To avoid anti-phishing techniques that scan websites for phishing-related text, phishers have begun to use Flash-based websites. These look much like the real website, but hide the text in a multimedia object.
Phone phishing
Not all phishing attacks require a fake website. Messages that claimed to be from a bank told users to dial a phone number regarding problems with their bank accounts.[45] Once the phone number (owned by the phisher, and provided by a Voice over IP service) was dialed, prompts told users to enter their account numbers and PIN. Vishing (voice phishing) sometimes uses fake caller-ID data to give the appearance that calls come from a trusted organization.
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