Technical Articles

Review Cloudmersive's technical library.

What is Bytecode Analysis?
10/26/2023 - Brian O'Neill

Bytecode is a representation of source code used in virtual machine-based languages like Python or Java, and it behaves like a set of instructions for the virtual machine itself. Because it’s neither source code nor machine binary, it’s often difficult for both traditional threat scanning software – or even human eyes – to effectively scrutinize. As a result, bytecode files present a unique attack vector for threat actors looking to slip malware into a target system undetected.


In the context of virus scanning, bytecode analysis is the process of analyzing bytecode files for threats. Real-world bytecode threats have included hidden programming methods designed to collect sensitive internal server information, and even commands to remotely download malicious content from external servers.

Effective bytecode analysis typically starts with disassembling executable files to retrieve bytecode instructions. Subsequently identifying threats within those instructions can involve a mixture of modern threat detection techniques. This can include anything from signature-based analysis (i.e., referencing a database of known bytecode threats) to behavioral analysis (i.e., threat sandboxing) or even heuristic analysis (i.e., rule-based threat detection).

Bytecode Analysis with the Cloudmersive Virus Scan API

The Cloudmersive Virus Scan API performs bytecode analysis – along with file hashing, signal extraction, pattern matching, heuristics, whitelisting & certificate analysis – as a baseline service in its sandboxing layer. This rigorous, dynamic approach to scanning helps ensure that hidden threats & zero-day threats are detected along with established threats.

It’s also possible to avoid files containing bytecode altogether using content verification functionality available via the Advanced Virus Scan API iteration. By setting custom file type restrictions in the Advanced Scan request body– particularly against scripts & executables – customers can mitigate unnecessary risks. In addition, customers can whitelist acceptable file types by extension in their request, ensuring only a specific number of approved file types pass their content verification check.

For more information on the Cloudmersive Virus Scan API, please do not hesitate to reach out to a member of our sales team.

800 free API calls/month, with no expiration

Get started now! or Sign in with Google

Questions? We'll be your guide.

Contact Sales