The Department of Homeland Security has promulgated new rules allowing much more likely deportation, by ICE (Immigration and Customs Enforcement) of any undocumented immigrant, except for those covered by DACA, which Trump is leaving in place, for now. NBC News has a typical story here.
In addition to people convicted of significant crimes or on watch lists (as under Obama), people only with arrests might be deported. Some observers say that when homes where all family members are undocumented are raided, all will be deported. Under Obama, people who had entered the country within the previous two weeks and were within 100 miles of a border were deported; now the period is two years and the territory, the entire U.S.
CNN reports an incident where a sexual assault victim was “reported” by her attacker.
There was also talk about asylum seekers. But this action so far seems to focus on people who ask for asylum right after entry at a border, which usually results in detention immediately. It is likely that it cracks down on bringing people across the border deliberately to then seek asylum (but this may have been illegal before). It does not sound likely that this affects people who later decided they could not return and who have been here a while, but it is still a very delicate matter.
Trump has not yet issued a revision of his January 27 Executive Order.
Update: Later Tuesday
Newsweek has a long article on how asylum seekers entering at the borders are likely to be handled now. A general tightening of what constitutes a credible threat of persecution is likely, but hard to assess with countries say, like El Salvador, with all the gang violence.