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Theoretical question: Is it possible, or will it ever be possible, for an attacker to sniff/intercept it and redirect a packet, sent from a client through wireless, modify it and then sent to the original intended server address with different values?

If so what are the ways to prevent it from happening or protect our data sent through wireless networks? Would it be using routers or Wireless external cards with better encryption measures?

For example, a packet telling X website that I want to write a text (Would it be possible for an attacker to sniff those packets, intercept it before reaching the destination and change the original text?). Or, a packet from an online client game where I'm playing telling the server that I got 100 health (Would it be possible for the attacker to change this packet before reaching its destination and modify it telling instead that I've got 0 health and then send to the server with modified values)?

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    search for MitM (man in the middle), then search for PKI used in TLS/SSL, that will show how to prevent a MitM. – Johnny Willer Jun 9 '15 at 17:31
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Yes, it's perfectly possible. The answer is to use encrypted connections, since encryption protocols such as TLS/SSL and SSH will stop the attacker from seeing what's in the packets, and also allow the server to detect and reject any changes from what was sent by the client.

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"Would it be possible for the attacker to change this packet before reaching its destination and modify it telling instead that I´ve got 0 health and then send to the server with modified values"

  • They could intercept and alter the packet easily, but forwarding the altered packet to the server without the server knowing it's come from another user is the challenge.

  • An ARP MITM attack could be used to convince the client that the attacker is the server and the server that the attacker is the client... hence acting as a man-in-the-middle with the ability to forward/alter/delete packets as the attacker wishes.

This is why encrypted connections (SSH, VPN, HTTPS etc) are much preferred over clear text communications.

  • Why is your first point a challenge? – schroeder Jun 9 '15 at 22:32
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This is a great question, because it highlights the importance of one of the three fundamental requirements of any secure protocol, i.e. integrity. (For the record, the other two fundamental requirements are secrecy and authenticity).

The goal of integrity is to prevent a man in the middle from altering the content of a message en route from the sender to the recipient.

The goal of secrecy is to prevent an eavesdropper or a man-in-the-middle from intercepting a message en route from the sender to the recipient.

The goal of authenticity is to ensure that the party on the other end of the connection is in fact who they claim to be.

If any one of these requirements is missing in a secure protocol, then the entire protocol breaks down and the protocol can no longer be trusted. Modern secure protocols such as SSL/TLS, SSH, etc., attempt to implement all three of the above requirements, and in most cases do it well if the protocol is implemented properly.

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