SharePoint has a hard limit of 50,000 unique permissions that can be defined per list and if your organization is of any significant size or (more likely) sees significant turnover, then you will hit that limit. Creating an automated solution to create Item-Level security will ensure that you hit that limit even faster.
The more complicated security is, the slower overall site performance becomes, indexing for search is also slowed and attempting to manage security in such a scenario is the stuff of nightmares.
It can be done (as Waqas pointed out) but if that really is the requirement then it is possible that SharePoint is not the best tool to accomplish what you are attempting to do.
If you are stuck in SharePoint-land for this then you would have to create some sort of custom front end that used custom CAML queries to call the back end data. Oh, and turn off indexing of the specific lists in the list settings so that they can't be found in a simple crawl.