Automated vulnerability scanners generate large quantities of false positives, resulting in a drain on resources as security engineers chase down bad leads. Nevertheless, the technology has value, as it is more cost-effective than constantly running penetration tests, according to a report in The Register today.

The report covers a session at the Nullcon security conference in Goa, India, where NCC Group security engineer Clint Gibler presented results from a recent test vulnerability scanning technology. In the test, Gibler used a scanner on 100 NCC customers across 10 industry sectors between February 2014 and May 2015. The scanner flagged approximately 900,000 potential vulnerabilities, the vast majority of which were false positives. Industry sectors experienced anywhere from an approximately 50 percent false positive rate to 89 percent in the most extreme cases.

Regardless, Gibler said scanners are still “worth it” for most companies, according to the article—in part because they “bridge the gap between expensive penetration tests.”