Many companies running BlackBerry Enterprise Server (BES) could be inadvertently opening a door to attackers, a penetration testing company has found.

Penetration testing consultancy NTA Monitor found that most of its customers running the BlackBerry Server with Microsoft Exchange were taking the path of least resistance by opening unencrypted ports from the heart of their network to service providers. The providers, in turn, opened a return back to the BES that would pass through firewalls without any policies being applied.

This left the network open on several levels, including session hijacking, IP spoofing, or just the interception of unencrypted traffic.

"A hacker could potentially use this back channel to move around inside an organisation undetected, removing confidential information or installing malware on to the network," said Roy Hills, NTA’s technical director.

According to NTA Monitor’s technical manager, Adrian Goodhead, the open configuration was no accident of poor implementation, accounting for a sizeable 10-15 of the company’s enterprise-level customers using BlackBerry handhelds (roughly 70-80 percent of the total base they surveyed). The commonest cause was simply cost.

The company recommends implementing a BES in a demilitarised zone (DMZ), which would isolate attacks against the sever from the wider network. However, this added complexity, and added complexity added expense.

"You have to add various software and hardware. People are trying to keep costs down," said Goodhead.

He characterised the flaw as low-to-medium in severity because "it requires a fair amount of knowledge" to exploit, but nevertheless one that needed to be addressed.

Goodhead criticised the service providers for not explaining that a more expensive implementation was usually necessary for security reasons. BlackBerry, for its part, gave details of how to implement its technology securely, he said, and so couldn’t be blamed.

NTA Monitor, which recently found holes in VPNs, offers several general security recommendations for clients using BES. These include using SSL encryption, enabling content protection on the handheld, disallowing non-approved applications – including P2P messaging – and turning off Bluetooth on the handheld.