In the context of network security
, a spoofing attack
is a situation in which one person or program successfully masquerades as another by falsifying data and thereby gaining an illegitimate advantage.
Man-in-the-middle attack and internet protocol spoofing
An example from cryptography
is the man-in-the-middle attack
, in which an attacker spoofs Alice
into believing the attacker is Bob
, and spoofs Bob into believing the attacker is Alice, thus gaining access to all messages in both directions without the trouble of any cryptanalytic
The attacker must monitor the packets sent from Alice to Bob and then guess the sequence number of the packets. Then the attacker knocks out Alice with a SYN attack and injects his own packets, claiming to have the address of Alice. Alice's firewall can defend against some spoof attacks when it has been configured with knowledge of all the IP addresses connected to each of its interfaces. It can then detect a spoofed packet if it arrives at an interface that is not known to be connected to the IP address.
Many carelessly designed protocols are subject to spoof attacks, including many of those used on the Internet. See Internet protocol spoofing
URL spoofing and phishing
Another kind of spoofing is "webpage spoofing," also known as phishing
. In this attack, a legitimate web page such as a bank's site is reproduced in "look and feel" on another server under control of the attacker. The intent is to fool the users into thinking that they are connected to a trusted site, for instance to harvest user names and passwords.
This attack is often performed with the aid of URL spoofing, which exploits web browser bugs in order to display incorrect URLs in the browsers location bar; or with DNS cache poisoning in order to direct the user away from the legitimate site and to the fake one. Once the user puts in their password, the attack-code reports a password error, then redirects the user back to the legitimate site.
Some websites, especially pornographic paysites
, allow access to their materials only from certain approved (login-) pages. This is enforced by checking the Referer
header of the [
] request. This referer header however can be changed (known as "Referer spoofing
" or "Ref-tar spoofing"), allowing users to gain unauthorized access to the materials.
Poisoning of file-sharing networks
"Spoofing" can also refer to copyright
holders placing distorted or unlistenable versions of works on file-sharing
networks, to discourage downloading from these sources.
Caller ID spoofing
In public telephone networks, it has for a long while been possible to find out who is calling you by looking at the Caller ID information that is transmitted with the call. There are technologies that transmit this information on landlines, on cellphones
and also with VoIP
. Unfortunately, there are now technologies (especially associated with VoIP) that allow callers to lie about their identity, and present false names and numbers, which could of course be used as a tool to defraud or harass. Because there are services and gateways that interconnect VoIP with other public phone networks, these false Caller IDs can be transmitted to any phone on the planet, which makes the whole Caller ID information now next to useless. Due to the distributed geographic nature of the Internet, VoIP calls can be generated in a different country to the receiver, which means that it is very difficult to have a legal framework to control those who would use fake Caller IDs as part of a scam
E-mail address spoofing
The sender information shown in e-mails (the "From" field) can be spoofed easily. This technique is commonly used by Spammers to hide the origin of their e-mails and leads to problems such as misdirected bounces (i.e. e-mail spam backscatter).
- "Pirates of the Digital Millennium" by John Gantz & Jack B. Rochester, 2005, FT Prentice Hall, Upper Saddle River, NJ 07458; ISBN 0-13-146315-2.