attack rating
Be careful with your wording. There is a difference between Attack (matrix attribute) and Attack Rating (used for edge distribution).
The book says IC use Host Rating x 2 for their Attack Rating (SR6 p. 186), but it is hinted that this will be changed to Host Attack + Host Sleaze.
IC damage seem to be Host Rating + Net Hits (SR6 p. 187, Black IC, Killer IC, Sparky IC, Sparky IC).
I have not seen that IC damage would be Attack/2 DV.