A new report out today shows that applications that use SSL are on the rise in the enterprise, and that even businesses that are aware of the risks introduced by SSL aren't necessarily aware of the scale of potential problems.

The findings from the 11^th annual Palo Alto Networks Application Usage and Threat Report show that around 34% of applications in use within the enterprise today use or can use the SSL to encrypt their traffic. Designed to survey the real applications running in the enterprise, it also shows the disparity between enterprise IT leaders' perception of their use of applications and the actual usage patterns or properties of applications scattered across organization. This year, the report studied 5,500 real-world environments and found approximately 2,100 applications running within these environments. Among those, 539 were SSL-capable.

As one of the core components of today's Internet ecosystem, SSL has greased the axle of Internet communication for key transactions like e-commerce and collaborative sharing applications, says Ryan Olson, head of threat intelligence for Palo Alto.

"Without having a sort of ubiquitous encryption protocol that is easy for people to implement, we wouldn't really be able to have any secure communication across the Internet," Olson says. However, the heightened level of privacy afforded by SSL encryption also brings with it a dark side.

"We certainly have a trade-off from a network perspective," he says, explaining that attackers increasingly use SSL to hide malicious traffic in plain sight from security inspection mechanisms. For example, he explains that variants of Zeus and other banking Trojans use SSL to hide command and control traffic from security devices. Similarly, the report pointed to the variant of the BlackPOS Trojan used to steal 100 million Target customer records, which used SSL to move information around using netbios shares and steal it through FTP.

"A lot of organizations are aware of this problem, but not as many as we think should be," he says. "The best way to deal with SSL is to do selective decryption of SSL traffic. We don't want to decrypt everything -- it's not really appropriate, and you don't want to invade the privacy of users in an inappropriate way. But many organizations don't do this for any applications at all. For applications which you have no idea what they are, you definitely want to have some visibility into what they are."

This is not a new problem, but it is a growing one as the number of SSL-capable applications rises within the enterprise. According to Palo Alto, the ratio grew by nearly 10 percentage points in the past year.

"I definitely don't see this decreasing over time, and it becomes even more difficult for organization as the total volume of SSL traffic increases. If you have a slice of your overall traffic you're ignoring because you're not inspecting it, as that slice grows larger the percentage of traffic that's going to include malicious behavior is going to increase proportionally," Olson says. 

Further increasing the threat is what Olson calls the long-term risks of Heartbleed, which are unknown and unpatched client-side applications vulnerable to the OpenSSL Heartbleed vulnerability. As he explains, many websites have gone through the proper stages of patching the vulnerability, reissuing certificates, and asking their users to reset their passwords. But there exists a whole world of client-side applications that organizations might not even know exist in their networks that could still be vulnerable to Heartbleed.

"Instant message application and any client-side application that could include some sort of browser in it might include OpenSSL," he says, "And it might be one of those 500-plus applications in the enterprises that can use SSL."

Palo Alto reported that "a lot of eyebrows were raised" as customers looked at the report's results. In many specific enterprise instances, the percentage of SSL-capable applications running in environments was much higher than 30%, sometimes pushing above 50% of applications in use.

"So, identifying all the applications in your network that are using SSL and figuring out if they use Open SSL is really the long tail of Heartbleed," Olson warns.