Say I am connecting to a server via SCP and copying some files from the remote server to my home computer. Can the server admins tell that I have copied something, see what was copied, or know who copied it?
A ServerFault question is almost identical to this. Hopefully you checked before posting your question, but yours is a little different so I will answer here.
The short answer is that if ANYONE has access and permissions to an endpoint (the system you are
scping from or
scping to), they can see what happens. If they do not have access to either endpoint, they likely won't have access to or be able to decipher what you're doing (apart from potentially knowing the application by protocol numbers).
The answer is ultimately very dependent on your infrastructure. Most likely though, as long as there isn't intense monitoring and SCP isn't considered at threat in the company (which will throw up red flags), your traffic will go by unnoticed. This is especially true for smaller companies.
As @SimonRichter mentioned: if someone can execute a command on your system (ie. admin or others), they can check your process list and see the command line
scp -args /filepath/. However this requires that they be either logging all process activity or checking it at the time you are transferring. Additionally, if you are doing it from your own system at work to another system (say at home or elsewhere), they won't necessarily have that visibility.
Additionally, as @alex.forencich mentioned: It is also possible to log all system calls (including file open and read calls) so even if your copying program (scp, sftp, etc.) does not log or leak anything (command line arguments), it is still possible to figure out what files were read or written. See the linux audit system. –
scp works with the help of code running on the server (
scp itself). That sever code is in theory completely in the control of the server admin, and the version of
scp running on the server to write the file down the connection to you, is separate from the version of
scp running on your machine to issue the request.
An administrator of the server could, just for an example, replace
scp on the server with a version that logs all requests, rather like a web server can write logs. Then they could see from those logs exactly what you copied.
Whether they have the expertise and the motivation to actually do this is less definite, but if they want to then in principle there's nothing to stop them.
I think these questions are companions to yours: https://security.stackexchange.com/questions/14782/is-there-an-easy-way-to-see-a-log-of-scp-activity-on-a-server-ala-var-log-secu, https://askubuntu.com/questions/659896/where-would-you-find-scp-logs
Although I don't know all the details, it seems that straight out of the box
sshd don't have options to log what you're asking about. So perhaps more is required than simple configuration, but you can't get away from the fact that admins control the server.
Anything that passes unencrypted through the memory of a computer can be read or changed by a sufficiently privileged user on that machine.
The names of running processes and the command line used to start them are accessible to any logged-on user on Linux. (This is not the case on Windows, for the curious.) Therefore, the admin or anybody else who happens to be around could see which files you copied. Additionally, it's entirely possible for the administrator to have set up some sort of file access logging, or to have replaced/jiggled the
scp program on one end to do extra logging.
scp just protects you from network sniffers. Obviously, both ends have to know the decrypted data, so there's the opportunity for a sophisticated admin on either of the endpoints to suck the data out of
scp's memory. Other solutions, even those that don't involve command lines, are also open to that: both ends of
sftp know what's going on, so it's possible to determine via memory inspection what
sftp is thinking/transferring.
A rule of thumb is, a person with root access can know everything (if he can be bothered to check). Probably the only thing that's off limits is a certificate-encrypted filesystem.
during the act, the
scp opens a process on the remote side, which can be seen by anyone just by invoking
ps. If you manage to hide the commandline showing up in the process list, then
lsof (list of open files) can show which files are being touched. It's so easy, I'm actually doing that to observe how far some copy process I started is, if I started the process on a terminal I can't view at the moment (where the file list is being output).
after the act, a quick scan with
find can find the newest files (if the timestamps weren't preserved during copy). If the files were accessed or touched in any way through a
ssh session, your
.bash_history shows what you were doing (but you can delete that if you want).
If security's meant to be very strict, you can always set up additional monitoring: you can listen to all file modifications with a simple daemon, and log everything about filesystem transactions, local and remote, doesn't matter. It wouldn't be a surprise to log all user-spawned processes. If backups are being done, the files may be still stored somewhere after you delete them.