Multiple flaws are endangering the software that runs the Internet's DNS (domain name system).

The vulnerabilities, discovered by researchers at Finland's University of Oulu, could be exploited to "cause a variety of outcomes," including crashing the DNS server or possibly providing attackers with a way to run unauthorized software, according to an advisory, posted Wednesday by the UK's National Infrastructure Security Co-ordination Centre.

Oulu researchers have created a DNS test suite that can be used to test for these vulnerabilities, and a number of DNS software providers, including Juniper Networks and the Internet Software Consortium have confirmed that some of their products are vulnerable.

The bug found in the Internet Software Consortium's BIND (Berkeley Internet Name Domain) software is "not considered high-risk," the group said. Hitachi and Wind River Systems have said that their products are not affected.

Microsoft, Cisco and Sun Microsystems are testing their products and could not immediately say whether customers would be affected.

Collectively the world's DNS servers manage the Internet's system for converting easy to remember Internet addresses, like, into the unique IP (Internet Protocol) addresses that are used by machines.

These servers have come under increasing scrutiny because recent attacks have shown how the DNS system could potentially be compromised to bring down a large number of Web sites.

Last month, VeriSign revealed that unknown attackers had used compromised computers and DNS servers to launch a denial-of-service attack against about 1,500 organisations.

Shortly after that attack was publicised, hackers attacked DNS servers at Network Solutions, and, a domain-name registrar based in Germany. Both of these events disrupted service to customers.

More information, including a list of vendor comments on these latest vulnerabilities can be found here.