Microsoft Knowledge Base Article 284947 contains the following summary:

The File Replication service (FRS) is a multi-threaded, multi-master replication engine that replaces the Lmrepl service in the 3. x and 4.0 versions of Microsoft Windows NT. Microsoft Windows 2000-based domain controllers and servers use FRS to replicate system policy and logon scripts that reside in the System Volume (SYSVOL) for Windows 2000-based clients and earlier.

FRS can also replicate files and directories between Windows 2000-based servers that are members of the same fault-tolerant Distributed File System (DFS) root or link replicas.

FRS initiates replication on "closed" files in directory trees in which replication has been enabled. Events that can trigger replication include the creation or deletion of a file, a version change to an existing file, or the resetting of permissions on a file or directory. This article describes the symptoms that occur when some antivirus programs that are not FRS-compliant perform virus scans on directories that host FRS-replicated files. Additional symptoms include:

Files in SYSVOL and DFS shares are replicated excessively with no apparent change to the files in those replica sets.
Files may replicate at off-peak hours, or at regularly occurring times if virus scans are scheduled to occur at specific times, or during periods of low server utilization.
The number of files in the staging directory constantly grows, perhaps emptying sometime after the virus scan program completes, or after the FRS schedule opens to allow replication.
The number of files in the staging directory constantly grows but never empties if changes to downstream partners cannot be replicated either because of network connectivity or an inability to process the number of modified files needing replication.
Network traffic between replication partners is consuming excessive network bandwidth and FRS is determined to be the responsible service.
One program that is known to reset security descriptors during virus scan is Norton AntiVirus (NAV) versions 7.0 and 7.5. Other virus checking programs that modify security descriptors during virus scans will result in the same symptoms.