The deal is expected to close within the next few weeks, and financial terms were not disclosed.
M86 Security Labs will be incorporated into the Trustwave SpiderLabs, which focuses on penetration testing, incident response, application security and security research.
Trustwave will also add the M86 Secure Web Gateway to its portfolio of Trustwave Managed Security Services. The company also plans to integrate M86 Security products into its cloud-based TrustKeeper portal.
M86 Security counts more than 25,000 enterprise customers, with 26 million users, in more than 96 countries.
In November 2008, Marshal and 8e6 Technologies merged. The following April, the company acquired start-up Avinti, maker of behavioral malware detection. Then, in September, the firm rebranded itself M86 Security. A year later, it acquired Finjan.
Trustwave also hasn't been quiet on the transaction front. In the past few years, it has bought web application firewall maker Breach Security, data leakage prevention provider Vericept and network access control vendor Mirage Networks. Last April, it filed for a $100 million IPO, but it postponed the move in August, citing market volatility.