CAPEC Details
Name Checksum Spoofing
Likelyhood of attack Typical severity
High Medium
Summary An adversary spoofs a checksum message for the purpose of making a payload appear to have a valid corresponding checksum. Checksums are used to verify message integrity. They consist of some value based on the value of the message they are protecting. Hash codes are a common checksum mechanism. Both the sender and recipient are able to compute the checksum based on the contents of the message. If the message contents change between the sender and recipient, the sender and recipient will compute different checksum values. Since the sender's checksum value is transmitted with the message, the recipient would know that a modification occurred. In checksum spoofing an adversary modifies the message body and then modifies the corresponding checksum so that the recipient's checksum calculation will match the checksum (created by the adversary) in the message. This would prevent the recipient from realizing that a change occurred.
Prerequisites The adversary must be able to intercept a message from the sender (keeping the recipient from getting it), modify it, and send the modified message to the recipient. The sender and recipient must use a checksum to protect the integrity of their message and transmit this checksum in a manner where the adversary can intercept and modify it. The checksum value must be computable using information known to the adversary. A cryptographic checksum, which uses a key known only to the sender and recipient, would thwart this attack.
Related Weaknesses
CWE ID Description
CWE-354 Improper Validation of Integrity Check Value
Related CAPECS
CAPEC ID Description
CAPEC-148 An adversary modifies content to make it contain something other than what the original content producer intended while keeping the apparent source of the content unchanged. The term content spoofing is most often used to describe modification of web pages hosted by a target to display the adversary's content instead of the owner's content. However, any content can be spoofed, including the content of email messages, file transfers, or the content of other network communication protocols. Content can be modified at the source (e.g. modifying the source file for a web page) or in transit (e.g. intercepting and modifying a message between the sender and recipient). Usually, the adversary will attempt to hide the fact that the content has been modified, but in some cases, such as with web site defacement, this is not necessary. Content Spoofing can lead to malware exposure, financial fraud (if the content governs financial transactions), privacy violations, and other unwanted outcomes.