  The principal mission of Multi-Source Multicast (MSM) is to disseminate all
messages from all sources in a network to all destinations. MSM is utilized in
numerous applications. In many of them, securing the messages disseminated is
critical. A common secure model is to consider a network where there is an
eavesdropper which is able to observe a subset of the network links, and seek a
code which keeps the eavesdropper ignorant regarding all the messages. While
this is solved when all messages are located at a single source, Secure MSM
(SMSM) is an open problem, and the rates required are hard to characterize in
general. In this paper, we consider Individual Security, which promises that
the eavesdropper has zero mutual information with each message individually. We
completely characterize the rate region for SMSM under individual security, and
show that such a security level is achievable at the full capacity of the
network, that is, the cut-set bound is the matching converse, similar to
non-secure MSM. Moreover, we show that the field size is similar to non-secure
MSM and does not have to be larger due to the security constraint.
