One of the most common security mistakes when building your MOSS farm is using the same service account for everything (Farm Admin, SSP, Application Pools, Search etc...).

The better practice is to create a separate service accounts for each segment in your SharePoint farm; so if you have already used one service account across the board; consider changing from a single service account to multiple:

What service accounts do I need and how do I change a service account in MOSS 2007? one might ask; the answer is simply posted on the following KB Articles:

Plan for administrative and service accounts (Office SharePoint Server)
http://technet.microsoft.com/en-us/library/cc263445.aspx

How to change service accounts and service account passwords in SharePoint Server 2007 and in Windows SharePoint Services 3.0.
http://support.microsoft.com/kb/934838