This appears to be the week of security acquisitions; following Dell's announcement that it intends to buy managed security provider SecureWorks on Tuesday, Sourcefire announced on Wednesday it has purchased antimalware maker Immunet for $21 million in cash.

Sourcefire, the creator of open-source intrusion prevention system (IPS) Snort, will add Immunet's cloud-based antimalware technology to its portfolio, company officials said. The acquired products will round out Sourcefire's offerings - which are currently comprised of Snort plus its Sourcefire 3D System that includes IPS, intrusion detection, SSL inspection, and netflow analysis -- with endpoint protection, reputation services, data-loss prevention and forensics. Sourcefire says that combining these acquired features with its existing capabilities offers customers comprehensive presentation against threats. What's more, Immunet's technology is delivered via the cloud, giving Sourcefire a cloud delivery system from which it can base future offerings.

"Immunet is a disruptive innovator in delivering cloud-based security solutions with over 750,000 users in 192 countries," said John Burris, CEO of Sourcefire, in a prepared statement. "This acquisition enables Sourcefire to accelerate our cloud initiatives and provides significant value to customers by protecting them against advanced client-side attacks. Immunet's technologies build upon Sourcefire's reputation for providing customers with innovative solutions that protect them from the latest threats."

Sourcefire says it will retain all of Immunet's full-time employees, who will be part of the company's newly formed Cloud Technology Group. Immunet was founded in 2008 by former Symantec executives. Its Protect 2.0 cloud-based antivirus download offers realtime protection against more than 14 million threats daily, according to officials. Of the $21 million paid for the acquisition, Sourcefire will deliver $17 million at closing and $4 million over the next 18 months, as product delivery milestones of Immunet's enterprise product are met, according to officials.

"Sourcefire is the perfect company to accelerate Immunet's path to market," said Oliver Friedrichs, Immunet founder and CEO, in a prepared statement. "Sourcefire secures organizations and individuals worldwide with advanced network security technology. Adding an internet-scale, advanced cloud platform catapults Sourcefire into a leadership position in endpoint protection as well."