the "professional" scammers aren't much better:

• In 2001, UBS sold 610,000 Dentsu-shares at ¥6, instead of 6 Dentsu-shares at ¥610,000. Even though the error was spotted immediately, the Tokyo Stock Exchange did not cancel the trades and UBS had to buy back the shares at market-value which caused them a loss of US$100m.
• In 2006, a fat-finger error by a trader at Mizuho Securities in Japan caused the firm to short sell a stock in an error that cost the firm ¥40 billion to unwind.
• In 2014, a Japanese broker erroneously placed orders for more than US$600bn (£370bn) of stock in leading Japanese companies, including Nomura, Toyota Motors, and Honda, which were subsequently cancelled.
• In 2015, a junior employee at Deutsche Bank whose superior was on vacation confused gross and net amounts while processing a trade, causing a payment to a US hedge fund of US$6bn, orders of magnitude higher than the correct amount. The bank reported the error to the British Financial Conduct Authority, the European Central Bank and the US Federal Reserve Bank, and retrieved the money on the following day.
• In 2015, the Investor Armin S. bought certificates from BNP Paribas at a price of €108 instead of €54,400 each. This caused a loss of €160m for BNP. The error was not detected because BNP failed to book more than 8000 trades for a whole week.
• In 2016, it was believed a fat-finger error caused the British pound to drop 6% in just a few minutes to US$1.1841, its lowest value for 31 years. A report by the Bank for International Settlements later concluded that the drop was not caused by a single factor.
• In 2018, Deutsche Bank mistakenly transferred 28 billion euros to one of its outside accounts, more than the bank's market value.