Around a third of anti-malware products fail to fully protect users of Windows 7 Professional, according to the latest test from Virus Bulletin.
The testing and certification organisation ran the Windows 7 test on 64 products, 20 of which failed to reach the required standard.
The testing team also found that some products had "serious issues with stability under pressure", according to John Hawes, anti-malware test director at Virus Bulletin.
"The level of quality seen in some products this month would be unacceptable in any software, and is especially unforgivable in security solutions," he said.
"Users need to be able to trust their security product, and to rely on it to keep them as safe as possible. That trust is as easily destroyed by flakiness and crashes as it is by failure to protect against malware or misdiagnosis of clean software as malicious."
Big names such as McAfee and CA were among the vendors whose products failed to pass the test.
McAfee's VirusScan Enterprise and CA's Internet Security Suite Plus and Total Defense r12 failed, while other poor performers included smaller vendors such as Lavasoft, Kingsoft and Comodo.
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