I would at minimum try grounding the phone line before it goes into the dsl
modem if you have access to it.
Phone lines aren't grounded.
This is a very good summary of the issues and a few partial solutions:
http://www.epanorama.net/documents/surge/telesurge.html
Note that none of the protectors are foolproof, if a common mode
surge of some magnitude occurs it can still fry any device connected
to the phone line.
Your best bet is to unplug the phone line if you hear thunder.
*************************************************************************
** List info, subscription management, list rules, archives, privacy **
** policy, calmness, a member map, and more at http://www.cguys.org/ **
*************************************************************************