According to research from AVG Technologies, malicious Web sites are on the rise, but the time those Web sites are online is declining.

InfoWorld reports that AVG is seeing between 200,000 to 300,000 new malicious Web sites per day. Nearly 70 percent of those sites are regular ones that have been hacked, but the remaining ones are custom-built.

The good news is that, of the custom-built sites, up to 94 percent are taken offline within 10 days, with 62 percent taken down in a day or less, notes internetnews.com.

Still, these short-lives sites are difficult to track and stop, says Roger Thompson, chief research officer at AVG. AVG expects the number of unique new sites linked to malware to grow exponentially.