wireshark -> tcpdump on dst=port# src = all
??


On Thu, Jan 30, 2020 at 1:13 PM Michael Eager <eager@eagercon.com> wrote:
When I look at /var/log/secure or run journalctl on my workstation, I
see failed SSH login attempts from a variety of IP addresses.  The
attempts are every 3-12 minutes.

/etc/ssh/sshd_config contains:
PasswordAuthentication no

The workstation is on a LAN behind an EdgeRouter firewall.  No Internet-
accessible ports are forwarded to the workstation.  The LAN has a
variety of servers, NAS boxes, WiFi access points, WiFi-connected
laptops, etc.

A typical /var/log/secure entry looks like this:
Jan 30 12:43:50 redwood sshd[21228]: Invalid user jackiehulu from
124.204.36.138 port 37394
Jan 30 12:43:51 redwood sshd[21228]: Received disconnect from
124.204.36.138 port 37394:11: Bye Bye [preauth]
Jan 30 12:43:51 redwood sshd[21228]: Disconnected from invalid user
jackiehulu 124.204.36.138 port 37394 [preauth]

The corresponding journalctl is:
Jan 30 12:43:51 redwood.eagercon.com audit[21228]: USER_ERR pid=21228
uid=0 auid=4294967295 ses=4294967295
subj=system_u:system_r:sshd_t:s0-s0:c0.c1023 msg='op=PAM:bad_ident
grantors=? acct="?" exe="/usr/sbin/sshd" hostname=124.204.36.138
addr=124.204.36.138 terminal=ssh res=failed'

I'm assuming that something on the network has been compromised,
allowing SSH login attempts on the LAN.  Other than turning off
each server/AP/laptop/etc, one at a time, to find when the accesses
stop, is there any way to find out where the SSH attempt is coming from?

-- Mike Eager
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