Microsoft VIA brings together a number of antivirus software vendors in an attempt to cut the spread of malware.
Fortinet's Global Security Research Team will help Microsoft address vulnerabilities and provide fixes to its customers more quickly.
"As cyber-criminals continue their unrelenting attacks, it is our responsibility as security vendors to work together to find innovative collaboration strategies and solutions," said Richard Stiennon, chief marketing officer at Fortinet.
"For this reason, alliances such as Microsoft VIA have become critical for all security customers, who rely on quick, efficient and effective identification of, and defence against, these attacks."
Stiennon explained that, as well as helping Microsoft, the partnership would allow Fortinet to protect its customers using Microsoft technologies.
Microsoft VIA provides the latest reports on medium and high severity viruses, as well as advice on how to prevent malicious attacks. It will provide information about specific viruses, and publish 'how-to' articles and links to other antivirus resources.
"Security is an industry-wide issue, and Microsoft remains committed to working closely with industry partners towards the common goal of improving security for all computer users," said Mark Miller, director of Microsoft's Security Response Centre.
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