- Confidential and Proprietary - Luminar Annual Threat Landscape Report Page 10 3.2 Technical Overview Like other messaging apps, Telegram allows users to send text and voice messages, make voice and video calls, share images, documents (2 GB per file), user locations, animated stickers, contacts, and audio files. In addition, Telegram has other distinct features: 3.2.1 Messaging Options Telegram offers its users several messaging options: + Channels – “one-to-many” channels offer one-way messaging where only admins can post messages. These channels, which can be either public or private and have an unlimited number of subscribers, allow administrators to send messages to everyone. The channels can be publicly available with an alias and a permanent URL so users can join. Once they join the channel, subscribers can see the entire message history. Any Telegram user can create a channel or subscribe to one. Furthermore, a channel can add a separate discussion group, which enables comments for messages posted on the channel. 21 + Group chats – have a maximum of 200,000 members and largely work in the same way as group chats on other messaging platforms. Group features include replies, mentions, polls, voice chats, video chats, admin tools, and statistics. Admin tools allow the addition of admins with specific privileges, such as managing communities, providing options to add new users, managing messages, blocking members, editing group info, and adding new admins. The statistics feature enables groups with over 500 members to view graphs pertaining to the group's activity and growth. + Chats between individuals- chats between individuals are also optional, providing features such as video calls and group voice conversations. In addition, users who are interested in further privacy can choose to conduct optional ‘Secret Chats’ with self-destructing messages, photos, and videos. These chats can only be accessed on the device that initiated the secret chat and the device on which the secret chat was accepted. Secret chats must be initiated and accepted via an invitation, upon which the encryption keys for the session are exchanged. Messages sent on secret chats can be deleted at any time and can optionally self-destruct. 21 https://telegram.org/faq_channels