That's correct; Telegram may not be as private as many users believe. While it's often marketed as a secure and private messaging app, its default settings and underlying architecture have key limitations that can expose user data. The main privacy concerns stem from its lack of default end-to-end encryption for all chats.

1. Lack of Default End-to-End Encryption
This is the most significant privacy issue. Unlike competitors like Signal and WhatsApp, Telegram does not use end-to-end encryption (E2EE) for standard chats, including group chats and public channels.

Default Cloud Chats: Messages in standard chats are encrypted in transit (client-to-server) but are stored on Telegram's servers in an encrypted format. This allows users to access their chat history from multiple devices, but it means Telegram holds the decryption keys. This creates a potential vulnerability where an attacker who compromises Telegram's servers could gain access to your messages.

Secret Chats: To use E2EE, you must manually start a "Secret Chat" with another user. These chats are device-specific and are not backed up to the cloud. They're also unavailable in group conversations.

2. Data Handling and Government Cooperation
While Telegram has a long-standing reputation for resisting government pressure, its policies have shown some evolution, and it does collect user metadata.

Metadata Collection: Telegram's privacy policy states that it collects metadata such as your IP address, device information, and a history of username changes. This data is used for security purposes and to prevent spam, but it could be used to identify and track a user's communication patterns.

Cooperation with Law Enforcement: In a significant policy reversal in late 2024, Telegram announced it would now share user data with law enforcement agencies in response to a valid legal order. This includes disclosing a user's IP address and phone number if they are suspected of criminal activity. Previously, the company only shared this information in cases related to terrorism.

3. Other Security Risks
Beyond the core encryption issue, other factors can compromise a user's privacy on the platform.

Vulnerabilities in MTProto: Telegram's proprietary encryption protocol, MTProto, has been criticized by security researchers for not being fully open-source, making it difficult for third-party experts to audit it for vulnerabilities.

Phishing and Malware: The platform has become a haven for cybercriminals, spammers, and scammers who use it to coordinate attacks, sell illegal goods, and distribute malware. Users can be tricked into giving away sensitive information or clicking on malicious links, compromising their devices and data.