debian mirror : Hash Sum mismatch

If deleting /var/lib/apt/lists/* does not work...
(esp. if you're behind a proxy), fix "Hash Sum Mismatch" like this:

Create file /etc/apt/apt.conf.d/99fixbadproxy
with this content

Acquire::http::Pipeline-Depth 0;
Acquire::http::No-Cache true;
Acquire::BrokenProxy    true;

See also here

I had a similar problem and it seemed to be a problem on the mirror.

As stated here remove the files "InRelease" on the server and try again.

In the /debian/dists/jessie directory there was a file called InRelease. It had a date several months back from the other files (which were mostly dated today's date).