This paper exploits co-channel interference (CCI) to secure the multi-antenna wiretap IFC consisting of two source-destination-eavesdropper triples, where each source-destination link is wiretapped by an external eavesdropper. To this end, we first propose a cooperative secrecy beamforming scheme, which is proved to be sufficient and necessary to achieve the secure degrees of freedom (S.D.o.F.) pair (1,1). By investigating the feasibility of the proposed beamforming scheme, we obtain the sufficient and necessary condition and also the beamforming vectors in closed-form to achieve the S.D.o.F pair (1,1). To the best of our knowledge, this is the first time that the benefit brought by CCI has been quantified.