first Let me explain regarding service tax- If the concern, from which you are taking security service, is a Company (as you mentioned ABC Ltd.) then you need not to pay any part of service tax. It would be applicable only if your security service provider agency would be Individual, HUF, Partnership Firm etc (but not Company).
As service tax is not payable by you so question of TDS on service tax does not arise.
If security service provider is Individual and you (you orgnisation)is company then you are liable to pay 75% of service tax (75% of 12.36%). and for TDS on this service tax, I think should not be applicable as TDS (contractor) is applicable on the amount payable for contract and not for tax. Over and above you are not paying service to the security service provider. You are not paying service tax on behalf of security service provider, it is your liability. But if you deduct TDS and deposit in govt account, it will not harm for anyone as security service provider will get credit of this TDS while filling his return.