This article examines the relationship between new information and communication technologies and territorial boundaries through an analysis of online interaction oriented around a sectarian interface in north Belfast. It is widely argued that new information and communication technologies are contributing to fundamental changes in the nature of territory and boundaries, with many arguing that they contribute to a deterritorialisation of social interaction. This article argues that new technologies neither transcend nor obliterate territorial boundaries but in certain senses reinforce and extend the role of physical boundaries as orienting locations for hostile interaction. Focusing on the interlinked territorial strategies of penetration and surveillance it argues that online interaction facilitates the extension and elaboration of territorial strategies oriented around physical lines of confrontation and the associated development of new material practices oriented around the physical boundary. (c) 2007 Elsevier Ltd. All rights reserved.