While the past five years of economic stagnation have hurt many industries, computer security has survived and, in many cases, thrived.

The managed security services market is a prime example: In 2011, the sector -- which includes everything from managed firewalls and intrusion detection systems to cloud security services -- grew by more than 21 percent to $2.8 billion in North America, according to estimates from business intelligence firm Gartner. The reasons for the growth depend on the customer who's buying, says Kelly Kavanagh, principal research analyst with Gartner. Midsize firms may be driven by compliance, while larger companies are looking to free up internal teams to improve security. Meantime, smaller businesses tend to have a stark choice: outsource security or struggle with a lack of funding and time.

"For those folks, it is not a matter of doing it inside the company or doing it with a managed security provider," he says. "It's about doing it with a managed service or not doing anything at all."

Analyst firms vary in their estimates of where the managed-security market will be in five years, but all agree it will grow. In 2016, the worldwide market will nearly double to $17.7 billion from $9.4 billion this year, according to Gartner. Market researcher International Data Corp. puts the number even higher, at $19.4 billion in 2016.

While compliance has fueled much of that growth, companies are increasingly focused on locking down their networks and data in the face of attackers who regularly succeed in breaching defenses. The complexity of the typical prescription for security -- defense-in-depth -- means that securing a company takes a lot more products than other information technology functions, says Christine Liebert, senior analyst of IDC's Security Services group.

"It's a big problem, and managed security services provide a way to tackle that," she says.

[ Cloud and managed security services are all the rage and help defend against denial-of-service attacks, but surrendering your data and applications to third parties comes with some risks of its own. See The Safety And Hazards Of Outsourcing Security. ]

Last week, managed security firm Trustwave boasted that its managed security services sales jumped nearly 150 percent between the first half of 2011 and the first half of 2012. The firm added the capability to manage two other security functions: Web application firewalls (WAFs) and security information and event management (SIEM). The more advanced services are necessary for customers that want to expand beyond more traditional fare, such as managed firewalls, log monitoring, unified threat management and secure email, the company stated in its release.

While reducing cost and complexity are both popular reasons for companies to approach a managed security service provider, increasingly MSSPs are encountering businesses that have just learned their networks are compromised and are looking for a specialist and partner to help them deal with the situation and improve their security. A significant number of prospective clients contact Dell Secureworks because of a compromise, says the company's chief technology officer, Jon Ramsey.

"It doesn't really matter if you are a large Fortune 50 company or a small-to-midsize company: You tend to look for security expertise because of the nature and sophistication of the problem," Ramsey says. "You know it's not your core competency and you don't want to do it yourself."

Finally, with security professionals increasingly wanting more information about the threats that are targeting their companies, being part of a managed security service means gaining the benefit of sharing information on threats. Such threat communities can give businesses early warnings when other companies in the same market are suffering from an attack.

"Even the large enterprises cannot get that information themselves," Ramsey says.

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