tug.ctan.org inaccessible on a specific machine

Nelson H. F. Beebe beebe at math.utah.edu
Fri Apr 2 17:27:37 CEST 2021

Stuart Little <achirvasub at gmail.com> reported yesterday on this list
that he was unable to reach tug.ctan.org from a machine in the
DigitalOcean cloud, and the block was still in place today.

I searched incoming connection logs at our site, and found no mention
of his address.  Next, I checked the campus boundary IP-blocked list,
and did not find it there either.

I then spoke to our departmental firewall administrator, and found
that machines in the DigitalOcean domain 142.93.*.* have been frequent
sources of ssh login attacks, and so a block against that IP space had
been imposed in our firewall.  The DigitalOcean block has now been
removed, but because of the attack patterns, may have to go up again.

This seems to be a common issue with virtual machines supplied by
various cloud services: good guys use them to do useful work at low
cost, but bad guys view them as an untrackable way to launch attacks.
At present, there does not seem to be a good solution to that problem.

- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -

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