Beverly Hills-based Hydra, an operator of a cost-per-action (CPA) advertising network, said today that it has linked with Aliso Viejo-based CitizenHawk, a provider of trademark protection and domain name services. According to the firms, the deal calls for CitizenHawk to offer "domain recovery services" to Hydra advertisers. CitizenHawk helps companies identify cybersquatters and others using brand trademarks, and recovers those domains for those brands, including going through all of the procedures required to reclaim those domains for advertisers. Financial details of the partnership were not disclosed.