Firewall Installation Invites DDoS Attacks

Thursday, February 10, 2011 @ 05:02 AM gHale

Safeguarding a system with firewalls only increases the risk of distributed denial of service attacks (DDoS) if improperly installed, according to a new report.

There is a tendency to deploy firewalls and intrusion prevention systems (IPS) in front of servers, the report said.

A survey of 111 global service providers uncovered a huge jump in DDoS attack size during the year, according to Arbor Networks. Maximum attack sizes reached 100Gbit/s for the first time, double that for 2009, and ten times the peak size seen as recently as 2005, increasingly in the form application attacks rather than simple packet flooding.

Attack frequency also appears to be increasing, with 25 percent of respondents seeing 10 or more DDoS attacks per month, and 69 percent experiencing at least one.

Service providers and companies could significantly reduce their DDoS vulnerability by designing their security infrastructure to better locate policy-based security devices such as firewalls, according to Arbor.

During 2010, nearly half of all respondents had experienced a failure of their firewall or IPS due to DDoS, something they could have avoided in many cases using better router security configuration.

“They [firewalls] should not be placed in front of servers. Folks do it because they have been programmed to do it,” said Arbor’s solutions architect, Roland Dobbins. In many cases, these devices became immediate bottlenecks in the face of DDoS, achieving the attackers’ aims with ease.

Firewalls and IPS were fine for LANs where they filtered outgoing traffic, but turned into obvious points of failure when used as a barrier to protect servers receiving large volumes of inbound packets, he said.

DDoS’ will continue to increase, despite the increased investment to fight DDoS’, Arbor said. Rather like the growth in spam after the advent of efficient filtering, better defenses force attackers to up their game, throwing more and more traffic at targets in the hope of having some effect.

An interesting blind spot suggested by Arbor could be mobile networks, which Dobbins describes as being almost “accidental ISPs.”

Currently, mobile providers know almost nothing about the state of the handsets using their services, despite half reporting security problems with customers. The same proportion reported outages due to security incidents, which suggests that such networks could become the next frontier for criminals to attack Internet targets.

“They don’t have visibility into their IP network. They are almost a decade behind,” said Dobbins of providers in this space.

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