Abstract: A mechanism for efficiently determining similarity between documents. A set of reference data items is generated by processing a reference document. A similarity index representing similarity between a candidate document and the reference documents is obtained by counting segments of the candidate document matching the reference data items. The candidate document is a message transmitted in a communication system where the message is compared against one or more reference documents representing unwanted messages to filter and block unwanted messages from being transmittal or propagated.

Abstract: A system differentiates good content from bad content in a user-provided content system. Messages are analyzed for features that characterize messages. A feature may occur in one or more messages. A feature that has more than a threshold number of occurrences in messages in a time interval is identified for further analysis. Enhanced authentication is requested from senders of the messages with occurrences of the identified feature. Based on the rate at which senders of the messages pass authentication, the content associated with the message is determined to be good content or bad content. Subsequent messages are blocked or successfully delivered based on whether features occurring in the messages are indicative of good content or bad content.

Abstract: A system differentiates good content from bad content in a user-provided content system. Messages are analyzed for features that characterize messages. A feature may occur in one or more messages. A feature that has more than a threshold number of occurrences in messages in a time interval is identified for further analysis. Enhanced authentication is requested from senders of the messages with occurrences of the identified feature. Based on the rate at which senders of the messages pass authentication, the content associated with the message is determined to be good content or bad content. Subsequent messages are blocked or successfully delivered based on whether features occurring in the messages are indicative of good content or bad content.

Abstract: A mechanism for efficiently determining similarity between documents. A set of reference data items is generated by processing a reference document. A similarity index representing similarity between a candidate document and the reference documents is obtained by counting segments of the candidate document matching the reference data items. The candidate document is a message transmitted in a communication system where the message is compared against one or more reference documents representing unwanted messages to filter and block unwanted messages from being transmittal or propagated.

Abstract: A data storage system includes a computer coupled to a non-volatile storage, such as a disk drive. The computer includes a block cache for storing cached copies of data blocks, and a hash table that stores hash values corresponding to the data blocks. Prior to writing back a modified cache block to the non-volatile storage, a log recorder of the computer stores an updated hash value corresponding to the modified cache block within a write-ahead hash log, which is also contained in non-volatile storage. The log recorder creates a log record including an updated hash value and an address corresponding to a modified cache block. The log recorder additionally maintains a first pointer value indicative of log records that have been stored to the write-ahead hash log, and a second pointer value indicative of the most recent log record stored in the write-ahead hash log for which a corresponding modified cache block has been stored to the non-volatile storage.

Abstract: A data storage system includes a computer coupled to a non-volatile storage, such as a disk drive, through an interconnect. The computer may include a block cache for storing cached copies of data blocks, and a hash table that stores hash values corresponding to the data blocks. Prior to writing back a modified cache block to the non-volatile storage, a log recorder of the computer stores an updated hash value corresponding to the modified cache block within a write-ahead hash log, which may also be also contained in non-volatile storage. In one particular implementation, the log recorder may create a log record including an updated hash value and an address corresponding to a modified cache block.