Sorry to revive a year old thread, but someone may find this useful.
The telnet login credentials for the Swann DVR4-1200 (and probably others) are:
username: root
password: 123456
I highly recommend that you login and change the password with the command: passwd
TBH I would not trust the security of this DVR.
Don't port forward directly to it. It has no encryption and will send your password in plain text.
If you want to securely connect from outside your LAN, buy a small office router with VPN capablities.