Flaws have been found in the software used to administer the internet's domain name system (DNS), with a number of supplier products at risk of security attacks.
The flaws were discovered by researchers at Finland's University of Oulu, and have been reported by the UK’s National Infrastructure Security Co-ordination Centre.
Juniper Networks has already confirmed that some of its routing products are affected, and Cisco is testing to see whether its product suite could be at risk.
Other firms, including Microsoft, are also carrying out tests on their products.
The flaws are in the Internet Software Consortium's BIND (Berkeley Internet Name Domain) software.
DNS servers convert text domain names into IP addresses to allow users to access the web pages they want.
Domain name registrars VeriSign, Network Solutions and Joker.com have all been targeted recently by remote attackers, who have used the DNS server network to launch denial of service attacks to take down company websites.