The founder of Cylance, Ryan Permeh, dismissed Sophos' claims.
"This conversation has gone on long enough and wastes everyone's time. We don't game tests and never will. We strongly urge customers to test any solutions on their own systems and networks. It is the only truly independent and “real world” metric that ever matters," Permeh wrote.
In a follow-up blog post, Cylance vice-president of product testing and certifications, Chad Skipper, claimed a test session had shown the company's product was able to stop all but 12 of 3700 malware samples.
Skipper said 460 of the 3700 malware samples had not ever been seen by "commodity antivirus".
Cylance has yet to make public the full test criteria and other details of the test.
The anti-virus vendor told Fortune magazine it has received some US$100 million in venture capital and counted more than 1000 customers, including 50 Fortune 500 firms.