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Cisco Releases Open Source Malware Signature Generator

Cisco’s Talos intelligence and research group announced on Monday the availability of a new open source framework designed for automatically generating antivirus signatures from malware.

The tool, named BASS, has been described as an automated signature synthesizer. The framework creates signatures from malware belonging to previously generated clusters and its main goals are to improve resource usage and make malware analysis easier.

Talos says BASS is designed to reduce the resource usage of Cisco’s ClamAV open source antivirus engine by generating more pattern-based signatures instead of hash-based signatures. The tool can also help reduce the workload of analysts who write pattern-based signatures.

The Python-based framework is implemented as a cluster of Docker containers, which makes it easily scalable, and it leverages web services to interact with other tools.

According to Talos, thousands of signatures are added to the ClamAV database every day and many of them are hash-based. The problem with hash-based signatures, compared to bytecode- and pattern-based signatures, is that a signature is used to identify a single file instead of an entire malware cluster. This has several disadvantages, including a bigger memory footprint.

Pattern-based signatures are easier to maintain compared to bytecode signatures, which is why Cisco prefers this type of signature.

The BASS framework takes malware clusters from various sources and each file is unpacked using ClamAV unpackers. Once the malware cluster is filtered to ensure that the files correspond to the input expected by BASS (i.e. Portable Executable files), the binaries are disassembled using IDA Pro or other disassembler, and the tool searches the samples for common code that can be used to generate the signature.

The source code for the Alpha version of BASS is available on GitHub. Cisco Talos will maintain the tool, but the company welcomes any feedback for improving its functionality.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.