This is due to a bug in SE4 v1.41 (and maybe previous Versions, too). After the first counter-intel project blocks an incoming intel, all other intel projects on the attacker's queue seem to slip through. I think you can block one attack per race.
MM knows about the bug, and hopefully it will be fixed in the next patch.
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"The Unpronounceable" Krsqk
Basic Tech Mod
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Basic Tech Mod v.75
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The Unpronounceable Krsqk
"Well, sir, at the moment my left processor doesn't know what my right is doing." -
Freefall