Blacklisting and Whitelisting

Malware-protection programs such as antivirus and antispyware software often use a technique referred to as blacklisting to protect computers. Programs that employ blacklisting allow everything to be stored on a computer other than files that are infected with threats listed on the blacklist. If a file is infected, these programs will either delete or quarantine it.

An emerging approach to combating malware is whitelisting. Whitelisting takes an opposite approach to blacklisting— that is, the protection program blocks everything except the files that are on its whitelist.

When it comes to protecting computers against the execution of unwanted malware, whitelisting is preferable to blacklisting. Whitelisting eases the life of the administrator, because in today’s interconnected world, users are typically allowed to run fewer applications than they should be blocked from running— including an almost unlimited number of unknown malicious executables that users might download from the Internet. However, whitelisting creates the risk of locking yourself out if you don’t use it properly. For example, you might neglect to add your management applications to the whitelist. In addition, you can inadvertently prevent your users from working if you forget to add one of their applications to the whitelist.

SRPs and AppLocker both support whitelisting and blacklisting, although they have different default policies. AppLocker uses whitelisting by default, thereby blocking everything; the administrator must explicitly define the applications that can run. The default SRP configuration uses blacklisting, which allows all applications to run; the administrator must define exceptions for any applications to be blocked.
Setting up whitelisting with SRPs is difficult, which is why most admins use it only for blacklisting applications. AppLocker is much better suited to provide whitelistingbased protection for controlling applications.

Source of Information : Windows IT Pro June 2010


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