That the U.S. is stocking its cyberarsenal should come as little surprise, but recent revelations from documents leaked by fugitive Edward Snowden revealed just how much.

Today, reports by The New York Times and The Guardian revealed that theNational Security Agency (NSA) and its U.K. equivalent, Government Communications Headquarters (GCHQ), have engaged in a long-running and wide-ranging effort to defeat the encryption widely used on the Web, including SSL, VPN technologies, and new protections used on 4G smartphones.

The disclosure follows the release of a mountain of information contained in documents leaked recently to The Washington Post that provide a peek at just how much the United States has embraced offensive cyberactivity -- something security experts say is likely to continue as other countries build cyberarsenals of their own.

"The best way I can explain why is to paraphrase a maxim echoed throughout history, which is: 'The best defense is a good offense,'" says Leo Versola, vice president of technology at security solution provider AhnLab. "Defense has always been much harder to successfully implement than offense for obvious reasons. However, I don't think this will necessarily change the way [the U.S. approaches] other countries suspected of conducting similar operations."

"Warfare," says Versola, "is shifting from a physical to a virtual battlefield and the rules of engagement are evolving."

According to documents obtained by The Washington Post, U.S. intelligence services carried out 231 offensive cyberoperations in 2011. In addition, under a $652 million project code-named GENIE, U.S. specialists broke into foreign computer networks and placed malware dubbed "implants" on tens of thousands of machines every year.

By the end of 2013, GENIE is expected to control at least 85,000 implants in machines across the globe -- roughly four times the number available in 2008, according to the U.S. intelligence budget. Many of the NSA implants are designed by the agency, but $25.1 million was set aside this year to make covert purchase of software vulnerabilities as well.

"Offensive cyberoperations will continue to play a key part of the government's strategy in the future; it only makes sense from a tactical and strategic perspective," says Rob Kraus, director of research with Solutionary's Security Engineering Research Team (SERT), adding that "disarming a country through the use of cyberwarfare can be very powerful and can be very effective without ever requiring boots on the ground."

Perhaps the most famous reputed example of America's offensive capabilities is the Stuxnet malware designed to target Iran as part of an intelligence effort code-named "Olympic Games." The operation has still not been officially acknowledged by the government despite The New York Times unmasking it in 2012. Snowden has also credited the United and Israel with creating Stuxnet.

The expansion of these activities is tricky given the lack of precedent and clear public lines of responsibility for the execution of direct cyberwarfare, says Philip Lieberman, president of Lieberman Software.

"Many existing branches of the military have undertaken an expansion of their missions into cyberwarfare, but details of actual operations are sparse," he adds. "The USA vs. China intelligence and cyberwarfare scenarios have been complex and opaque, with both sides accusing the other with both having difficulty in attribution of actions to either side. Welcome to the world of the other side being a friend and enemy simultaneously."

The use of cyberweapons by the U.S., however, comes with a major drawback: the prospect of another country returning the favor, says Kraus.

"One thing to consider is that we are one of the best-connected countries in the world, which also provides our adversaries with a larger base of targets to choose from and cause harm to the U.S.," he says. "So it is not all about offense, but defense must be considered. This is why it is important for the U.S. to continue spending on protecting critical infrastructure."

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