\k{config-ssh-bug-ignore1} and possibly \k{config-ssh-bug-plainpw1}.
\H{errors-crc} \q{Incorrect \i{CRC} received on packet} or \q{Incorrect
-MAC received on packet}
+\i{MAC} received on packet}
This error occurs when PuTTY decrypts an SSH packet and its checksum
is not correct. This probably means something has gone wrong in the
error message whether the problem is in the client, in the server,
or in between.
+In particular, if the network is corrupting data at the TCP level, it
+may only be obvious with cryptographic protocols such as SSH, which
+explicitly check the integrity of the transferred data and complain
+loudly if the checks fail. Corruption of protocols without integrity
+protection (such as HTTP) will manifest in more subtle failures (such
+as misdisplayed text or images in a web browser) which may not be
+noticed.
+
A known server problem which can cause this error is described in
\k{faq-openssh-bad-openssl} in the FAQ.