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# Blacklist Jar Feature

Support for blacklisting signed jar files has been added to 6u14. A blacklist is a list of signed jars that contain serious security vulnerabilities that can be exploited by untrusted applets or applications. A system-wide blacklist will be distributed with each JRE release. Java Plugin and Web Start will consult this blacklist and refuse to load any class or resource contained in a jar file that's on the blacklist. By default, blacklist checking is enabled. The `deployment.security.blacklist.check` deployment configuration property can be used to toggle this behavior. The blacklist is updated using the property deployment.blacklist.url which defaults to https://javadl-esd-secure.oracle.com/update/blacklist.

The blacklist entries are the union of the blacklist files pointed to by the `deployment.system.security.blacklist` and `deployment.user.security.blacklist` properties. By default, `deployment.system.security.blacklist` points to the `blacklist` file in the `jre/lib/security` directory, and `deployment.user.security.blacklist` points to a blacklist file that contains additional entries added by a user.

The blacklist is a text file with the following format:

        attribute : value

Each jar file on the blacklist is identified by the `x-Digest-Manifest` attribute where `x` is the name of the `MessageDigest` algorithm, and the value is the base64 encoded hash value of the Manifest. Comments are denoted by lines starting with the # (number) symbol.

Here is an example:

        # Buggy Utilities, version 1.0
        SHA1-Digest-Manifest : QONXbQg+EtNOguIOAgpUUOadhv8=
        # Malware Inc., version 99.99
        SHA-256-Digest-Manifest : SewaudBCZ3iXt1KX0BeFHpQiiM1xYLtvLw3Ow2RJfcs=

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