Abstract  Globally, the number of Smartphone users has risen  above a billion, and most of users use them to do their  day-to- day  activities.  Therefore,  the  security  of  smartpho nes  turns  to  a  great  concern.  Recently,  Android  as  the  most  popular  smartphone platform has been targeted by the attack ers. Many severe attacks to Android are caused by m alicious applications  which  acquire  excessive  privileges  at  install  time.   Moreover  some  applications  are  able  to  collude  tog ether  in  order  to  increase  their  privileges  by  sharing  their  permissi ons.  This  paper  proposes  a  mechanism  for  preventing   this  kind  of  collusion  attack on Android by detecting the applications whi ch are able to share their acquired permissions. By applying the proposed  mechanism  on  a  set  of  290  applications  downloaded  f rom  the  Android  official  market,  Google  Play,  the  number  of  detected  applications  which  potentially  are  able  to  conduct  malicious  activities  increased  by  12.90%  in  compare   to  the  existing  detection  mechanism.  Results  showed  that  there  were   4  applications  among  the  detected  applications  which  were  able  to  collude together in order to acquire excessive priv ileges and were totally ignored by the existing method.   

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[25] Zhou Y., Zhang X., Jiang X., and Freeh V., Taming Information-Stealing Smartphone Applications (on Android), in Proceedings of the 4th International Conference on Trust and Trustworthy Computing , Pittsburgh, PA, USA, pp. 93-107, 2011. Iman Kashefi received his MS degree in computer science at Universiti Teknologi Malaysia (UTM) in the field of information security in connection with the years of related work experience in IT Development Center of Iran. The Best Student award of the UTM was granted to him and he was honored to receive the Pro-Chancellor award among the eight best PhD and MS graduates of the UTM. He received his Bachelor s degree in the field of computer engineering from Islamic Azad University of Tehran and has published Journal papers in the field of network security and Android security. Along with conducting research on smartphones security, currently he works as Solutio n Manager in Mobile Communication Company of Iran (MCCI). Maryam Kassiri is a lecturerat Islamic Azad University (IAU), lecturing under the Department of Computer and Information Technology. She received her MS degree in Management of Information Technology from Payam-e-Noor University, and her BS degree in Information Technology Engineering from Islamic Azad University. She also serves as an IT expert in the eLearning sector of IT Development Center of Iran, affiliated to Industrial Development and Renovation Organization of Iran. She has published some Journal and Conference papers related to her research works including eLearning and Network Security. Preventing Collusion Attack in Android 727 Mazleena Salleh is an associate professor at Universiti Teknologi Malaysia (UTM), lecturing under the Department of Computer Science, Faculty of Computing. She has taught several courses in the area of computer hardware system, cryptography and computer security. She received he r PhD in Computer Science at UTM in the field of computer networking while her Master s degree from Virginia Polytechnic State University in the field of electrical engineering. She has published several journal and conference papers related to her research works that include watermarking, steganography, chaos image encryption, network analysis, e-learnin g and knowledge management. Her current research is on computer security related issues namely data survivability and availability in cloud, elliptic curve cryptography, body sensor network and detection of misuse in computer forensic.