Increasing attention is being paid to reliability, safety, and security issues in social systems. Scott Sagan (2004) examined why more security forces (a redundancy solution) may produce less security (redundancy problems). In that paper, he discussed how the system could cause backfire in three major ways (i.e. “common mode error”, “social shirking”, and “overcompensation”). Using Sagan’s hypotheses, I simulate and analyze a simplified and generic security system as more guards are added. Simulation results support two of the hypotheses, showing “common mode error” makes the system backfire, and “social shirking” creates inefficiency in the system as well as exacerbating the common mode error’s effect. Simulation results show “overcompensation” has no effect on backfiring, but leads the system to a critical situation, in which it could easily be affected by “common mode error.” The structure of the model and simulation results give some insights into developing appropriate security policies.