Behavior whitelisting is a security method in which permissable actions within a given system are specified and all others are blocked. The method may be conducted through security software or the addition of whitelisted exceptions to a behavior blacklist.
Behavior whitelisting is used to secure websites, services and forums from bots and hackers, computers from malware and hacking attempts and email from spam and phishing attempts. Whitelisting is also used in the breach detection systems (BDS) protecting networks.
The two traditional ways of blocking spam are are content-based filtering and IP-based blacklisting. These methods are becoming less effective as spammers find ways to get around them. Blocking all behavior not on a whitelist can provide very effective security. However, it requires knowledge of what tasks and communications a system will need to perform and must be adjusted when these requirements change.
Whitelisting behavior can also be very effective in spam prevention. The method works well when the types of email sent and received are not so varied and unpredictable as to be outside of a whitelist, causing false positives. Formal email procedures can facilitate whitelisting behavior. Whitelisting commonly saves CPU and memory resources as the list of allowed behaviors is almost always smaller than is the case in a blacklist and therefore less work to scan through.
If improperly implemented, behavior whitelists can create vulnerabilities. Whitelisting is most effective where the number of required allowable functions are few and security requirements and accessibility are high. A blacklist used in this situation requires more set-up time and maintenance work to block the high volume of more varied behaviors. Blacklists also require more comprehensive and up-to-date knowledge of threats. Both methods must be implemented scrupulously to provide adequate security.