Runtime packers are a widely-used technique in malware today. Virtually every Win32 malware added to the WildList as well as ad- and spyware is packed with one or another runtime packer. Not only can they turn older malware into new threats again, but they might also prevent AV vendors from using more generic approaches and therefore requiring more work, which possibly generates more errors or broken updates, unless the product is able to handle all the different runtime packers out there.