Firewalls can pose a security threat as they age, due to the number of admins that manage them and the chance that default or open passwords have been used, says Pentura.

According to the security assessment company, firewalls are typically managed by a succession of admins who create their own rules, which then accumulate over a period of years. This creates rule duplication, which can impinge on performance, but also brings risks such as the use default or open passwords.

Worst still, because some staff with access to the firewall console will have been from partners and third party organisations, old rules can leave a trail of security holes that go unnoticed by the staff that succeed them.

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The company estimates that the average company of 5,000-10,000 seats, will have anything between 200 and 600 rules per firewall, more if multiple devices is taken into account. The commonest problem will simply be excessive use of the same policies.

Understanding the web of sometimes complex rules was extremely difficult to do, more so for staff not steeped in the subtleties of a particular platform.

"Above 100 rules it starts to get harder," said Pentura's R&D director Simon Morris. "Rules get added rather than taken away."

With this in mind, Pentura has developed a new service it claims can strip out the risk posed by out-of-date rules.

Pentura uses an automated tool for a first-run analysis, which forms the basis for a manual assessment of where the overlaps and possibly security problems might lie, said Morris. The main platforms encountered by the company were Cisco, Check Point and, even years after its disappearance, Netscreen, which demonstrated the length of time 'geriatric' firewalls were being kept in service.

The service is restricted to conventional packet firewalls, but the company is looking at how this concept might be extended to application and unified threat management (UTM) devices in the future.

The Firewall Risk Assessment service, including remediation, starts at £5,000 for a single cluster - usually two devices - with economies of scale as more firewalls are added.

See also: Yoggie launches open source portable firewall