Organizations and companies with integrity concerns for their archivals are currently left with very few and unconvenient solutions. To cope with those needs, a Time Stamped Virtual WORM system has been proposed previously, but only its concepts and theory have been examined yet. Hence, this paper focuses on defining practical block formats to help implement this system in reality. But there are several pitfalls on the path of implementation, and this paper has to be extremely cautious not to introduce any limit - or security flaw - into virtual WORMs. With such requirements, two different block formats are successfully defined: a streamed format where security data is inserted within user?s documents, and a detached format where security information is written in a different location. Finally, the detached format is studied in the sample case of a tamper-evident FTP server.