One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified y-ray sources (UGSs). Despite the large improvements of Fermi in the localization of y-ray sources with respect to the past y-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of y-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the y-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic y-ray source. With this new IR diagnostic tool, we searched for y-ray blazar candidates associated to the UGS sample of the second Fermi y-ray catalog (2FGL). We found that our method associates at least one y-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to y-ray sources in the 2FGL catalog. Show Partial Abstract