Police officers dealing with cyber crimes said people sharing their phone numbers at shopping malls to win discount coupons or with ‘friends’ they have met only on social media are more likely to become victims of cyber fraud.

“If you don’t want to receive fraudulent calls and get duped, don’t share your phone numbers at random,” said a senior officer of Kolkata police.

A large number of people who go out shopping are approached by various brand representatives or retail outlet officials to share personal contact details. Many fill in forms and share details hoping to win lucky draw prizes or to get a credit card.

A number of people register their details thinking that is mandatory.

“It is very important for people to be cautious and choosy about whom they are sharing their phone numbers with in any public place. People may approach you for details so you can participate in a lucky draw or with offers of a zero-interest credit card, but one should remember that sharing personal information in a public forum only makes us more vulnerable to cyber frauds,” the officer said.

Similarly, many do not hesitate to share their numbers with ‘friends’ they meet on social media but later end up being duped.

Calls asking for bank details or text messages telling recipients to urgently pay electricity bills are some of the tricks fraudsters try to extort money, the police said. In many cases, fraudsters make WhatsApp video calls, take screenshots of the call and replace the caller’s photograph with that of a nude woman or man and use it to blackmail the victim.

According to officers at Lalbazar, the number of cases of ‘sextortion’ has increased in the city in the last few weeks.

“It is like a honey trap. First, the fraudsters befriend their potential target through social media and then try to initiate video calls either through social media messenger or WhatsApp. Once the call is received, screenshots of the conversation are captured and the picture of the person who initiated the call is replaced with a nude photograph to make it look like the recipient was having an objectionable chat. Then the person is blackmailed with the screenshots and forced to pay up,” said an officer.

An officer who had dealt with such cases said: “The majority of such cases are not reported formally as the victims fear embarrassment. While probing the cases that are reported, we come to know that the victims participated in video chats with people they had interacted with only on social media. One should be discreet while sharing personal details,” the officer said.

Phone numbers shared on a public forum could be misused and are often illegally procured by fraudsters involved in various forms of cyber crimes.

An officer said leakage of personal data is one of the primary reasons for the mushrooming of cyber frauds.

“Phone numbers either shared by mistake by the victim or accessed by fraudsters through organised rackets active in the Dark Web lead to cyber frauds. We always try to create awareness so that people are not fooled into sharing their personal details,” said the officer.