Over 1300 previously delisted domains were found once again to be rated by malicious by google. Many of these domains “pop up” for a while to spread their “badness”, and then “lie low” under the radar , only to come alive again once delisted.
Accordingly, these domains have been relisted, as well as “promoted” to the “immortals” or domains which have been consistently associated with malicious activity.
List of “immortal” malware domains is here: http://mirror3.malwaredomains.com/files/immortal_domains.txt.
A “psychohistory” of these long-lived malicious domains would be interesting and we’d be happy to help with any of those research efforts.