This article studies five category of malicious cyber activities against space assets in order to assess to what extent the existing international telecommunications law and space law address such activities and identify which rules should be pursued to effectively solve them. Five category of such activities include jamming, hijacking, hacking, spoofing, and robbing the control of telemetry, tracking and control (TT&C) of a satellite (a kind of anti-satellite (ASAT)). Actual incidents are selected for analysis. Those are: (i) jamming: Iranian deliberate harmful interference to the Eutelsat satellites solved in the ITU; (ii) hijacking: a terrorist organization, Liberation Tigers of Tamil Eelam (LTTE) hijacking US Intelsat-12 satellite solved by diplomatic negotiation between the Sri Lankan and US Governments using international telecommunications law developed by the ITU and individual national laws; (iii) hacking: alleged Chinese hacking of US NOAA’s information systems; (iv) spoofing: Iranian spoofing of the GPS signals to guide a US/CIA’s RQ-170 UAV into the Iranian territory; and (v) robbing the control of TT&C: alleged Chinese taking control of US remote sensing satellites including Landsat-7 and Terra AM-1. Concluding remarks include: 1) international telecommunications law developed in the ITU can adequately address harmful interference or hijacking as a result of malicious cyber activity as long as that is conducted by a non-State actor; 2) efforts have started in the ITU to strengthen its fact-finding ability in line with the TCBM measures taken in space activities. This orientation may be remembered as a beginning of the new stage that international space law and international telecommunications law would be merged into one field of law: 3) It remains unclear about the implications of an intangible damage occurred to a satellite when its TT&C is robbed of as a result of malicious cyber activity, while it is clear that such an action constitute the violation of the principles of respect for state sovereignty, national jurisdiction and non-intervention. Thus, for promoting peaceful uses of outer space, the elaboration of relevant Articles of the Outer Space Treaty is urgently needed to formulate clear conditions for national space activities.