He had wanted to "clean up" his computer's hard drive, but what it cleaned out instead, was his bank account.
The total losses suffered? Some $45,000 — about half of his savings.
The 71-year-old retiree, surnamed Chen, told Shin Min Daily News that the incident occurred in January this year.
Chen shared that he'd received a call from a bank on the morning of January 31, informing him of the dozens of suspicious transactions which took place in the wee hours of the night.
A total of 47 transactions had been made from 2am, before the bank froze the account.
Checking through his statement, Chen saw that the amount transferred out of the account each time was no more than $1,000.
He suspected that this was because transactions above $1,000 would have triggered a notification from the bank, and noted that the outcome might have been worse if the bank had not stepped in.
The cybercriminals had taken a total of about $37,000, Chen revealed. The account had contained more than $90,000 initially.
Chen made a police report the next day, and suspended his credit card as well as all digital banking services.
However, sensing something amiss, Chen went to check on two other bank accounts which were under his name. It was then that he realised $8,000 had been taken from one of his accounts through 27 fraudulent transactions.
Downloaded 'disk cleaning' tool
Following his, Chen recalled downloading a programme from an online advertisement about two weeks before the incident.
He told Shin Min Daily News that a notification had popped up on his computer screen two weeks earlier informing him that his computer was running at slow speeds.
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He also ended up downloading a hard disk cleanup and data optimisation tool which it advertised.
However, Chen deleted the programme the same day after getting annoyed by the constant pop-up notifications.
He added that police suspect that this could have been how his credit card details were stolen.
Chen revealed that the two bank accounts affected contained his retirement funds and were the ones he used most regularly.
With his savings reduced by about half as a result of the incident, he shared that it has caused him considerable anxiety and he has no choice but to return to work.
"I'm currently working part-time as an industrial management supervisor. Now that this has happened, what can I do? I just have to go out and work to earn some pocket money."
According to Shin Min Daily News, police have confirmed the incident and said that investigations are ongoing.
Chen hopes that his experience serves as a warning to others to be careful when downloading programmes from the internet.
He added that his case is still being investigated by the bank, but he has also filed a dispute with the Financial Industry Disputes Resolution Centre in hopes of receiving some compensation from the incident.
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candicecai@asiaone.com