who vs whom

In my opinion, you don't need to use "whom." I would write it like this:

A former financial consultant with OCBC Singapore cheated five clients out of $170,000 in fake time deposits, targeting clients not technologically savvy enough to recognize the fraud being perpetrated against them.

I'd vote for "who" if you had to use it.

I agree. Whether whom is technically correct or not, nobody really uses it anymore.

You'd use 'whom' whenever you'd use 'them'. With whom were you talking? I was talking to them.

But, again, today we would just say, "Who were you talking to?" "Whom" is anachronistic (old-fashioned, out of date).

Years ago, when applying for jobs, our cover letters used to be addressed: "To Whom It May Concern" (if you didn't know the person's name), but I haven't applied in a job in so many years, I have no idea whether that's still done, or even whether cover letters are still in vogue. But that was the only time 'whom' was really used.