Spying isn't like the movies. Most of it comes down to hacking (theft), bribery, and blackmail.

Example case study of an Israeli operation. Israelis create a shell business, funneling deals and money to a wealthy Arab businessman with many government contracts and contacts over multiple years. The Arab feels comfortable with the business arrangement, and he makes a lot of money on the deal! One day, the Israeli "businessman" meets him in a public place. Nothing suspicious or underhanded. During the meeting, an envelope, a briefcase, whatever, is exchanged. The entire meeting is being recorded by Israeli intelligence.

Now comes the blackmail. Does this Arab want everyone to know that he's conducting business with Israelis? With Israeli spies?? If that goes public, he's going to lose his connections with the government, he's going to lose his business with Arabs who hate Israel, and the Israelis will dump him in a heartbeat.

So, maintain the status quo. Except now the Israelis want him to start feeding them information he gets from his friends in the Egyptian government. At first it's harmless unimportant information. Except that every time he passes on some information, just to maintain the status quo, he gets deeper and deeper in. Now not only does he have to worry about losing his business, he's straight up breaking the law.

In the US, we have the example of Aldritch Ames. A CIA official who passed on some low-value intelligence to Russians for a quick buck to get out of debt. But once that first action was taken, the other agency has all the power.

Same for prostitutes/honeypots. Once you can get someone to take that first step, you have leverage.