Dirtside SLAMs

On page 9 of the Dirtside rules, it states that SLAMs
"cannot be 'spoofed' by ECM or Stealth systems."

Does this mean that the defender's die type against a
SLAM attack is the Basic signature?  I could not find
any other mention of this in the rulebook.  We have
been using effective signature, but a clarification would
be helpful.

Jon Davis