portage/rsync question

Hi.  I have a security-related question for Portage/rsync: 

 

If someone makes a change to a copy of a program (say a backdoor added to
apache) hosted on a public mirror, will the sync'ing between the public
mirror and the main rotation mirror determine that it's corrupted (via 'bad'
checksum) on the public-mirror side and replace it? 

 

Thank you in advance,

-john