OLSR and security

For MANET, there are several security problems to be considered. Some of these issues are special problems related to the physical nature of the wireless links in the networks. Others are security problems, which also exists in the (wired) Internet.

Being a proactive protocol, OLSR periodically diffuses topological information. Hence, if used in an unprotected wireless network, the network topology is revealed to anyone who listens to OLSR control messages. In situations where the confidentiality of the network topology is of importance, regular cryptographic techniques such as exchange of OLSR control traffic messages encrypted can be applied to ensure that control traffic can be read and interpreted by only those authorized to do so.

In OLSR, each node is injecting topological information into the network through transmitting HELLO messages and, for some nodes, TC messages. If some nodes for some reason, malicious or malfunction, inject invalid control traffic, network integrity may be compromised. Examples of situations that may occur due to lack of data integrity functionality, are:

1. A node generates TC messages, advertising links to non-neighbor nodes.

2. A node generates TC messages, pretending to be another node.

3. A node generates HELLO messages, advertising non-neighbor nodes.

4. A node generates HELLO messages, pretending to be another node.

5. A node forwards altered control messages.

6. A node does not forward messages as required by OLSR.

7. A node forwards broadcast control messages unaltered, but does not forward unicast data traffic.

8. A node ``replays'' previously recorded control traffic from another node.

Authentication of the originator node for control messages (for situation 2, 4 and 5) and on the individual links announced in the control messages (for situation 1 and 3) may be used as a countermeasure. However, to prevent nodes from repeating old (and correctly authenticated) information temporal information is also required, allowing a node to positively identify such delayed messages.

OLSR is highly vulnerable to attacks directed at availability. Such attacks are referred to as a Denial of Service (DoS)[43] attacks. An attacker could launch OLSR packets containing false information in large amounts. This could lead to a situation where processing of this data could claim all resources on the receiving nodes, leaving them not able to handle any other tasks. Eventually the OLSR service could crash leaving the node not available. Integrity mechanisms can prevent an untrusted node, not having access to the key used, from performing such an attack.