of domain names, which is both a domain URI Blocklist and RHSBL. It lists spam domains including spam payload URLs, spam sources and senders ("right-hand side"), known spammers and spam gangs, and phish, virus and malware-related sites. It later added a zone of "abused URL shortners", a common way spammers insert links into spam emails. The Botnet Controller List (BCL) was released in June 2012 and is a list of IP addresses. It lists IP addresses of which Spamhaus believes to be operated by cybercriminals for the exclusive purpose of hosting botnet Command&Control infrastructure. Such infrastructure is commonly used by cybercriminals to control malware infected computers. The Composite SnowShoe (CSS) is an automatically produced dataset of IP addresses that are involved in sending low-reputation email. Listings can be based on HELO greetings without an A record, generic looking rDNS or use of fake domains, which could indicate spambots or server misconfiguration. CSS is part of SBL. The Spamhaus White List (SWL) was released in October 2010 and was a whitelist of IPv4 and IPv6 addresses. The SWL was intended to allow mail servers to separate incoming email traffic into 3 categories: Good, Bad and Unknown. Only verified legitimate senders with clean reputations were approved for whitelisting and there were strict terms to keeping a Spamhaus Whitelist account. The Domain White List (DWL) was released in October 2010 and was a whitelist of domain names. The DWL enables automatic certification of domains with DKIM signatures. Only verified legitimate senders with clean reputations were approved for whitelisting and there are strict terms to keeping a whitelist account. Spamhaus also provides two combined lists. One is the SBL+XBL and the second is called ZEN, which combines all the Spamhaus IP address-based lists. Register of Known Spam Operations The Spamhaus Register of Known Spam Operations (ROKSO) is a database of spammers and spam operations who have been terminated from three or more ISPs due to spamming. It contains publicly sourced information about these persons and their domains, addresses and aliases. The ROKSO database allows ISPs to screen new customers, ensuring that ROKSO-listed spammers find it difficult to get hosting. A listing on ROKSO also means that all IP addresses associated with the spammer (their other domains, sites, servers, etc.) get listed on the Spamhaus SBL as "under the control of a ROKSO-listed spammer" whether there is spam coming from them or not (as a