An Android phone on my network keeps connecting to a malicious site

My wifes phone keeps reaching out a malicious site (udmserve.net), and it is being blocked by my router's Trend Micro network scanner. I ran Trend Micro's virus scan, as well as Clean Masters, but there are no results on her phone. Any idea of how to fix this? I enabled real-time protection from Trend Micro as well. It's a Samsung Galaxy Halo, which is a low-end Galaxy.