1. A method for computer security, comprising: receiving content including potentially malicious executable code (“CODE-A”), intended for downloading at a client computer; scanning CODE-A to derive a profile thereof; determining, based on the derived profile of CODE-A, an appropriate computer account from among a plurality of computer accounts, under which CODE-A may be processed by the client computer, wherein each computer account of the plurality of computer accounts has associated therewith a security context within which an executable run under such account is processed; combining (i) information about the determined computer account name and (ii) CODE-A, with (iii) executable wrapper code (“CODE-B”) into combined code (“CODE-C”); and forwarding CODE-C to the client computer for processing.