Online security experts on Wednesday said crudely written appeals for help have begun to appear in email boxes, asking for donations through a website or an offshore bank account.
"It's only a matter of time. We have fully fledged websites that spoof well-known charities, for example," said Paul Wood, chief information security analyst at MessageLabs, an internet security company.
Aid organisations have collected millions of dollars through the internet since 26 December - the day the tsunami struck several Indian Ocean nations and claimed about 150,000 lives.
"It is a good opportunity for the criminals out for a quick buck, and it is something that people are going to respond to," said Forrester Researcher analyst Jonathan Penn.
"We have fully fledged websites that spoof well-known charities"
The fraudulent appeals are patterned after two existing scams: "Phishing" attacks that direct people to legitimate-looking websites in order to trick them into giving up their credit card numbers, and 419 scams, messages that promise great riches in exchange for a bank account number.
"We have been rendered homeless and have lost all we have in life. We will be very grateful if you can assist us with any amount of money to enable us to start a new lease of life," one message said.
Ken Dunham, malicious code intelligence manager for the internet security company iDefense, said such scams could be very effective.
"It is a get-rich quick thing, and it makes perfect sense in light of the disaster. Everybody's heard of it, they all know lots of people have died off, maybe whole families have died off, and monies truly are available," Dunham said.