A new study by security vendor Damballa hammers home yet again why companies that rely solely on antivirus technologies as a first line of defense against new malware threats are making a mistake.

Between January and October last year, the company tested four popular antivirus tools to see how quickly they would detect files that had already been identified as malicious by Damballa using its threat detection service.

On average, 70 percent of malware threats remained undetected by the AV products one hour after Damballa had identified them as malicious and 34 percent were able to slip past the AV products even 24 hours later. Seven percent of the malware products detected by Damballa did not have an AV signature a full month later and in some cases malware files remained undetected for more than six months.

For its study, Damballa says it systematically kept rescanning files that were missed by the AV tools to see how long it would take for the files to be detected as malicious. In the real world, each file would have been scanned just once, which means that a lot of malicious code is able to penetrate enterprise networks before AV tools are able to detect and block them.

As a vendor of a malware detection service, Damballa may have a stake in playing up deficiencies in AV technology. But concerns about the effectiveness of signature-based malware detection tools in blocking new threats are certainly not new.

In a similar exercise last year, malware researchers at Lastline Labs studied just how quickly AV tools could detect new malware threats. The researchers studied the tools for one full year and discovered that on any given day, new malware slips past 50 percent of virus scanners. Even after two months, one-third of all antivirus scanners failed to detect much of malware samples. Detection rates on average tended to increase sharply in about two weeks after a new malware sample is released suggesting a "common lag time" for antivirus vendors, Lastline had noted.

Over the period of the year-long study, not one antivirus scanner had a single day in which it caught every new malware sample, according to Lastline. The study showed that while antivirus technology is not dead, it is having an increasingly hard time keeping up with threats.

The numbers are disturbing considering the huge volume of malware threats hitting enterprise networks on a daily basis said Damballa CTO Brian Foster.

He pointed to recent research conducted by Ponemon Research on behalf of Damballa showing how businesses on average receive nearly 17,000 malware alerts each week or roughly 2,340 alerts daily. More than 80 percent of these alerts are typically filtered out as being unreliable or as false alerts and just about 4 percent of the alerts are actually investigated by security teams.

The sheer volume of potentially malicious files hitting enterprises daily and the relative slowness with which AV tools are able to spot these files puts enterprises at risk because it means malware is dwelling in their networks undetected for long periods, he said.

The massive intrusion at Target in 2013 is a prime example of this. The retailer has acknowledged that it could have prevented the intrusion had it paid more attention to the numerous alerts being generated by its malware detection systems. According to the company, its security team ignored the alerts on the assumption that the alerts were unreliable.

The shortcomings of signature-based antivirus tools have prompted security analysts to call for multilayered defenses to detect and block threats at the perimeter and inside the network. Though many consider AV products as inadequate against new threats they still advocate its use in blocking known threats.  However, companies should consider complementing the products with other approaches such as dynamic sample analysis and network anomaly detection, Lastline had noted.