Worldwide security software revenue totaled $22.1 billion in 2015, a 3.7% increase in from 2014, according to Gartner, Inc.

Security information and event management (SIEM) remained the fastest-growing segment in 2015, with 15.8 % growth, while consumer security software showed the sharpest decline at 5.9% year-on-year. In 2015, the top five vendors together accounted for 37.6% of the security software revenue market share, down 3.1 percentage points from 2014. These vendors also displayed a collective decline of 4.2% in 2015, while the rest of the market (Others) grew strongly at 9.2% year-on-year.

"The below-market growth seen by these large vendors with complex product portfolios is in contrast to the market growth and disruption being introduced by smaller, more specialized security software vendors," said Sid Deshpande, principal research analyst at Gartner.

Symantec maintained the No. 1 position despite the company suffering its third consecutive year of revenue decline and its highest decline in revenue over a three-year period. Its security software revenue declined 6.2% to $3.4 billion. In 2015, 74% of Symantec's revenue came from the consumer and endpoint protection platform (EPP) categories, which collectively declined 7% year-on-year and were a major contributor to Symantec's revenue decline.

Intel’s security software revenue also declined in 2015, with revenue falling 4.1% to $1.75 billion. Once again, the decline in the consumer and EPP markets, which accounted for 75 percent of Intel's revenue in 2015, contributed in large part to Intel's revenue decline. IBM was the only one of the top five vendors to show growth. IBM’s security software revenue grew 2.5% to total $1.45 billion in 2015. IBM's growth was driven by its positive performance in the SIEM segment and its significant services business, which generates revenue for its product business.