root kit detection/penetration

[cdewitt () indepthsec com]

What are the best practices for penetration testing the viability of placing root kits on a client's external servers - 
vpn, web, app...?

And, while I'm asking - what are the best practices or countermeasures for root kit placement?

What root kits are still viable/current?

All comments/tomatoes welcome...cd

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