AVG is upgrading the LinkScanner component of Anti-Virus Free Edition 8.0 following reports that the security suite was placing heavy demands on the websites it scans.

Linkscanner, which checks the validity of links on web pages, has caused problems for some website publishers who found it hit their sites repeatedly, using their bandwidth and leading to a sudden spike in visitors.

It includes a feature called Search-Shield, which checks search-engine results returned by downloading and scanning the web pages indexed, and warns the user if a site contains a security threat.

But Search-Shield's scan is recorded by many web analytics programs as a visitor. Worse yet, website owners complained that Search-Shield presented itself to websites as Microsoft's Internet Explorer (IE) 6.0 browser, making it difficult to filter AVG scans from legitimate visitor traffic in their logs.

LinkScanner masked itself as IE 6.0 so as to not tip off bad websites to a scan, since malware writers have been known to engineer websites to behave differently depending on a user's IP address or the browser they are using.

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Search-Shield will no longer scan every result in the way that caused traffic numbers to skyrocket, said AVG marketing manager Lloyd Borrett.

Anti-Virus Free Edition 8.0, released in April and the first one to incorporate LinkScanner, has been downloaded millions of times, according to AVG's website. The current trouble apparently wasn't unexpected, just not expected quite so soon, according to a statement on the site.

"Because of the unique nature of our technology - we scan web links before our customers open them to ensure they are safe - we anticipated that we would see a spike in the number of sites that were analysed. However, we underestimated the popularity of our product and the resulting number of verdicts that came back to us," the statement said. "As a result, we did not anticipate seeing the volumes we have seen in two months for another 24 to 36 months."

Borrett said he didn't how LinkScanner has been fixed, but that it may no longer scan every result, instead checking the search-query results against a blacklist, or a list of known bad sites.