Service of Claim Forms can be effected on unknown parties, but there are pitfalls to avoid.  As financial institutions and corporates increasingly face threats from unknown parties, particularly in the context of cyber incidents, a number of recent decisions in the Supreme Court and the Commercial Court provide a timely reminder of the importance of effective service, and the steps that the courts will consider sufficient in order for service to have been deemed effective, particularly in situations where the defendant(s) may be unknown or may be seeking to evade service.  Parties facing these threats will benefit from a familiarity with the current landscape and rules as we enter the new decade which will undoubtedly see a continued rise in the need to serve unidentified defendants.