I'm using avast! Internet Security 7.0.1426 on Windows XP Pro SP3, and I noticed a problem with the File System Shield's transient caching. Every time a file is renamed, AIS scans the file (no matter how many times AIS has already scanned the file). This may not be a problem if you're renaming a 20KB or even a 1MB file, but when you're renaming a 2GB self-extracting 7-zip archive, it effectively locks up Windows Explorer for anywhere from 30 seconds to 2 minutes or longer (until AIS finishes scanning the file).
Here's what I did:
1. I created a self-extracting 7-Zip archive (filename "c:\backups\inh.exe", size 2.05GB).
2. I renamed the file from "inh.exe" to "inh-20120418.exe". AIS scanned the file, using filename "inh-20120418.exe".
3. I renamed the file from "inh-20120418.exe" back to "inh.exe". AIS scanned the file again, using filename "inh.exe".
According to Sysinternals' Process Monitor, Windows Explorer is using operation SetRenameInformationFile to rename the file (it's not opening the file and writing its contents to a new file), so why is AIS scanning the file, especially when it just finished scanning it? I can understand why it would scan the new filename if I was copying the file, but I'm not. I'm not copying anything, I'm not opening anything, and I'm not writing anything; I'm only renaming the file (basically, Windows is just updating its directory index to change the file's name).
For what it's worth, this same behavior occurs if I rename the file from the command prompt.
Transient caching may work in terms of not scanning a file multiple times if you open the file without renaming it, but transient caching does not appear to work when you rename a file.
