<Page> Exhibit 21.1 SUBSIDIARIES OF DIGITALNET HOLDINGS, INC. DigitalNet, Inc., a Delaware corporation DigitalNet Government Solutions, L.L.C., a wholly owned subsidiary of DigitalNet, Inc., a Delaware limited liability Company Federal Systems Integration Corporation, a wholly owned subsidiary of DigitalNet Government Solutions, L.L.C. and a Virginia Corporation Getronics Government Solutions Puerto Rico, Inc., a wholly owned subsidiary of DigitalNet Government Solutions, L.L.C. and a corporation organized under the laws of Puerto Rico HFS GmbH, a wholly owned subsidiary of DigitalNet Government Solutions, L.L.C. and a limited liability company organized under the laws of Germany