Server hardening, network protections, anti-virus software, strong passwords, ... are all important facets in protecting your information. Most people depend on their web hosting provider for basic security even though shared environments depend on a high level of trust between users and administrators.
Add-on capabilities like those offerred by OSSEC provide several important protections that are accomplished using agentless monitoring. Agents offer a wider range of capability at the cost of maintaining them as part of system upgrades. While this adds cost, it also adds tha ability to intervene early when a change occurs rather than after you recognize that real, and sometimes irreparable, damage has been done.
See this File Integrity piece: https://www.advancedsecuritydefenses.com/2011/10/control-file-integrity-monitoring.html#
Getting serious with dedicated infrastructure?
https://www.advancedsecuritydefenses.com/operations/
