Twitter CEO Jack Dorsey highlights dangers of 'SIM swap' fraud

But Ori Eisen, founder of Arizona-based security firm Trusona, which specializes in authentication without passwords, said the rapid fix should not be seen as an answer to the broad problem of SIM swap fraud.

"The problem is not over," Eisen said, noting that these kinds of attacks have been used to take over other high-profile social media accounts and for various kinds of fraud schemes.

Eisen said it's not clear how many people are attacked in this manner but that automated technology can create billions of calls that lure people into giving up information or passwords.

Some analysts say hackers have found ways to easily get enough information to get a telecom carrier to transfer a number to a fraudster's account, especially after hacks of large databases which result in personal data sold on the so-called "dark web."

"Mobile accounts' text messages can be hijacked by sophisticated hardware techniques, but also by so-called 'social engineering' -- convincing a mobile provider to migrate your account to another, unauthorized phone," said R. David Edelman, a former White House adviser who heads a cybersecurity research center at the Massachusetts Institute of Technology.

"It only takes a few minutes of confusion to make mischief like Dorsey experienced." Thousands of these attacks have been reported in countries where mobile payments are common, including in Brazil, Mozambique, India and Spain.

Researchers at the security firm Kaspersky say security systems by many mobile operators "are weak and leave customers open to SIM swap attacks" especially if the attackers are able to gather information such as birth dates and other data.

In a recent blog post, Kaspersky researchers Fabio Assolini and Andre Tenreiro said some cases come from cybercriminals paying off corrupt employees of mobile carriers -- for as little as $10 to $15 per victim.

"The interest in such attacks is so great among cybercriminals that some of them decided to sell it as a service to others," the researchers wrote.

In Brazil, some criminals have taken over victims' WhatsApp accounts, using it to ask the person's friends for "urgent payment," Assolini and Tenreiro wrote.

"This is a pretty ripe avenue for fraud," said Joseph Hall, technologist at the Center for Democracy & Technology in Washington.

Hall said some carriers are using artificial intelligence to separate the legitimate SIM card replacements from fraud, but that this has not been universally deployed.

"I would blame the carriers for not having more robust ways to authenticate users," he added, while also calling on Twitter to offer better safeguards.

A faked tweet from the president or other prominent person could lead to "devastating consequences," such as a plunge in financial markets, Hall said.

"This kind of thing becomes hard to counteract, because even after the information comes out that it's a hoax, people may not believe it," he said.

The Dorsey case, Hall said, highlights the need for better forms of authentication, especially for large online platforms like Facebook and Twitter where messages can have an impact.

This could involve a physical key that plugs into a device or a software-based system such as Google Authenticator, Hall noted.

Eisen said that paradoxically, the push for longer and more complex passwords has led to greater use of insecure text messages for authentication.

"The security practitioners must come to terms with the fact that what used to work doesn't work now," he said.

"We need to look for solutions that are not so easily exploited by bad guys and are easy for people to adopt.