If somebody cheats and lies to get a job will his income be halal?

One of my friends is feeling very tormented by his past.

There are various instances in his past where he has committed cheating which keeps tormenting him and making him question if the job he is doing is Halal or not.

1. During his graduation days, in his final project submission he did not contribute much to the group project but got credit for the same because of the good performance of my group. This also resulted in him getting a first division in my final graduation marks.

2. During the entrance exam for management, he cheated for a few marks which might be one of the reasosn he made it to a prestigous institute

3. During job interview, he has told few lies about his experience, which would have been a major factor in himt getting the job.

Keeping in mind the above factors, he keeps thinking whether the earnings from hs job is halal or not.

Please advice.