Juniper Networks (NYSE: JNPR) fleshed out its security portfolio late last week, paying $10 million for Webscreen Systems, a subsidiary of Accumuli, a U.K.-based IT security specialist, as confirmed by the companies.

The acquisition gives Juniper a distributed denial-of-service (DDoS) entry for Web applications and web sites in its security lineup and complements its $80 million purchase last year of Mykonos Software and an earlier $95 million acquisition of Altor Networks for virtualization security.

“DDoS attacks on data centers continue to increase in both scale and complexity—ranging from massive volumetric attacks to sophisticated and difficult-to-detect advanced persistent threat (APT) attacks,” wrote David Koretz, Juniper counter security vice president and general manager in a blog post. “Webscreen has developed a track record for its unique behavior-based approach to DDoS mitigation that effectively protects against both high volume and APT attacks.”

Accumuli initially gained Webscreen through its acquisition of Boxing Orange in April, 2011. According to terms of the transaction, Accumuli will remain a Webscreen reseller. Webscreen currently employs four people–three technicians and one sales and management person–and all will carry their existing roles to Juniper.

Gavin Lyons, Accumuli chief executive, said that Juniper’s experience, reputation and channels to market, made the deal attractive.

“The sale of WSL assets gives us substantial resources to continue growing our market share in the IT security sector by concentrating on what we are good at–identifying and being highly proficient in best-of-breed security technologies, expanding on our managed security services portfolio, building security intelligence platforms and creating complementary intellectual property along the way,” said Lyons, in a statement.

Koretz added: “The acquisition of the Webscreen DDoS capability gives Juniper another asset to help protect our customers and their data centers. Webscreen’s unique, fully automated DDoS protection system assists in keeping our customers websites and web applications highly available.”