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What if you're offered up to 300,000 won ($224) to make a simple delivery of a shopping bag to someone?

Doing this three or four times a day easily makes a daily income of well over 1 million won.

Isn't it a great way to make quick cash?

This line of thinking, unfortunately, is how many international and exchange students in Korea fall victim to voice phishing scams, according to Zhang Xujuan, a manager in the international trade business department at Woori Bank.

Zhang is an anti-voice phishing scam instructor. The Chinese national gives workshops at universities in her mother tongue on how to recognize and avoid voice phishing scams.

"Many international students end up criminally charged or deported, in the worst-case scenarios," she said.

As benign as their motives may be, the act of delivering a bag full of cash to a person who later turns out to be a member of an organized voice phishing ring constitutes fraud, a criminal charge that can result in many years in prison.

Zhang Xujuan / Courtesy of Woori Bank

More concerning is, according to her, the students almost never see the harm in withdrawing millions of won in cash from a bank's ATMs and putting it in a bag to hand it over to someone they don't even know.

"Students in their early to mid-20s have no stable income. They are easily tempted by the prospect of making quick money, since working part-time jobs at coffee houses or restaurants is not as lucrative and far more demanding," she said.

"I make sure I let them know about the consequences of what they thought was nothing more than running an errand, helping them avoid the pitfalls in the first place."

Also among the most frequent incidents leading to criminal investigations is using unauthorized entities or individuals when exchanging foreign currency to the Korean won — linked almost always to tuition payments.

University tuition is a large sum of money for international students. The offer of even a slightly favorable exchange rate goes a long way to reduce the burden of coming up with millions of won — however small the difference may be.

Chinese students in Korea, for example, arrange a deal with a Chinese broker. The student pays in the Chinese currency to the broker in China, who then wires Korean won into the account of the student. This will have the student's account frozen. The account holder will be referred for disciplinary actions of the university. No less probable are police questioning and prosecution.

"Sometimes the students face suspension or forced leaves, if their accounts were found to be involved in a scam. Claiming ignorance of the situation will not help at this point," she said.

Calls from individuals impersonating embassy personnel of their countries are not easy to dismiss, either.

"The students tend not to be dismissive of the calls from the embassy as they would those from the police, the prosecution or financial authorities. As soon as they hear the word embassy, they think the call would be relevant to their stay here."

She had cases where a student thanked her for giving the workshop. That student recognized a call from a phishing scam ring after the voice on the phone asked to press zero.

"Had she complied, it would have emptied her bank account with her personal information handed over in full through a button-activated phishing app. Cases similar to this occur more often than people realize."

She plans to give workshops at least once every two months.

"I think what I do is best encapsulated by the saying, 'An ounce of prevention is worth a pound of cure.' I am committed to preventing rather than dealing with regretful consequences after the fact," she said.

Recently, Woori Bank rolled out a product whereby account holders of the bank can be insured for up to 3 million won lost in phishing scams for a period of one year. Subscriptions can be made during an in-person visit at the branches of the lender.