Updated Friday, Apr. 3, 2009 at 1:37 p.m. EST

Internet Explorer's (IE) market share has dropped consistently over the past 12 months, according to new data.

While IE still dominates the browser market, its hold has slipped by about one percent or fractions of one percent almost every month for the past year. In fact, IE's market share dropped from 73.7 percent last March to 66.8 percent this month, according to data from web metrics company Net Applications.

“It's hard to know exactly why users are switching browsers without asking them -- but I would imagine a number of them are concerned about using the ‘default' browser that many cybercriminals have attacked in the past,” Graham Cluley, senior technology consultant at security firm Sophos, told SCMagazineUS.com Thursday in an email.

Despite the release of IE8 on March 19, the browser's market share dropped from 67.4 percent in February to 66.8 percent in March. But, during the last week in March -- when IE8 was available -- IE's market share held steady, Vince Vizzaccaro, vice president of marketing at Net Applications, told SCMagazineUS.com Thursday.

While IE's foothold has slipped, other browsers have seen gains over the past year. Mozilla Firefox jumped four percent during the past year, from about 18 percent last March to about 22 percent this month. Similarly, Apple's Safari browser increased from having about six percent to about 8 percent over the same period.

“I think there's growing awareness that alternatives are out there,” Cluley said. “As more people grow more appreciative of alternative browsers, it makes it tougher for Microsoft to convince them there is a compelling reason to stick.”

In Europe, IE7 already has been surpassed, according to web analytics firm StatCounter. For the first time last week, Firefox 3.0 became the most popular web browser, overtaking IE7's weekly market share.

“The move is partly explained by a small switch from IE7 usage to IE8 but also by growing market share overall by Firefox 3.0," Aodhan Cullen, CEO and founder of StatCounter, said in a statement. "The data shows that Firefox is closing the gap and is now just 10 percent behind all IE versions in Europe.”

A Microsoft spokeswoman told SCMagazineUS.com Friday in an email that the company does not comment on usage share reports but said that usage share tracking must be viewed within a broad context since it is subject to swings based on geography, time zone and enterprise usage during working hours.

Users perhaps are choosing alternate browsers to avoid mainstream attacks, but doing so does not ensure security, Cluley said.

“Using a different browser doesn't mean you are immune from attack, but it might mean you are less commonly targeted,” he said.

Microsoft, meanwhile, has not stood silently by. The company had outfitted IE7 with a phishing filter and IE8 comes bolstered with a cross-site scripting filter, clickjacking prevention, and per-site ActiveX, which enables users and administrators to manage where an ActiveX control can run.

As the market shifts, cybercriminals will try to abuse a wide variety of web browsers -- many already have chosen to not just solely focus on IE, Cluley said. And users must realize that malware does not have to exploit a software vulnerability to infect a system. Many attacks succeed because of social engineering, not a browser flaw.