An update to CA's eTrust anti-virus software started registering alerts for genuine files on a number of applications, including its own programme code.
Kaspersky Lab's Internet Security application, meanwhile, falsely flagged up HSBC's online banking portal as infecting users with a copy of the HTLM-Agent-CE Trojan.
According to Techworld UK, CA's software misbehaved after update number 33.3.7051 was downloaded by the eTrust application and a further update - 34.0.0.6674 - has now been released.
Affected users are also being offered a download tool that 'de-quarantines' the false positive files on any system affected by the problem.
Computer Associates has apologised to its software users and is referring them to the following site for further information.
Kaspersky Lab, meanwhile, had a bad Monday on the support side of things, after its Internet Security software falsely alerted users that HSBC's personal internet banking site had been infected with malware over the weekend.
Veteran information security company Kaspersky reportedly moved swiftly to rectify the problem with its software as soon as problem was discovered.
The solution appears to have centered on a forced update to the software, Infosecurity notes.