New Delhi, Oct. 23 -- Markets regulator Securities and Exchange Board of India (Sebi) on Thursday cautioned investors against fraudulent WhatsApp stock-tip groups that use 'astroturfing' - fake endorsements and profit claims - to create a false impression of credibility and lure investors.

In a statement, Sebi said certain unregistered persons were offering stock recommendations to investors through invitation-only WhatsApp groups in the name of free investor education. The operators of these fraudulent groups often use overseas WhatsApp numbers posing as market experts, PTI reported.

"To make these calls look credible, certain members, acting in concert with the operators, post false claims of profit and praise the 'expert'. This pract...