b _ o
First letter: transfer mode
a = ascii
b = binary
Underscore:
A letter in this position would indicate any special operations, like gzipping or tarring the data on-the-fly. "_", meaning "no special operation".
Second letter: transfer direction
i = input (= upload = FTP PUT)
o = output (FTP GET)
r ftpmurmy
Third letter: access mode
a = anonymous
g = guest user
r = regular user
After this letter is the username of the person performing the operation.
ftp 0 * c
"ftp 0 *": service name, authentication method and authentication user id (if applicable). These are not configurable in vsftpd, so this is a constant string that carries no useful information. It is there only to match wuftpd log format.
The last letter: completion status
c = completed
i = interrupted (transfer failed)
**********************************
What has happened is he took a copy of the ssl_request_log-20100528.gz file... twice... then uploaded one back and reaplced the one he took.
Depending on his role it could just be that he is archiving your logs and taking a copy for backup. I am not sure why he would PUT the file back. He could have modified it for less than pure reasons.
I don't know your relationship or dynamics so it is hard to say what his intentions are.