  We consider gossip networks consisting of a source that maintains the current
version of a file, $n$ nodes that use asynchronous gossip mechanisms to
disseminate fresh information in the network, and an oblivious adversary who
infects the packets at a target node through data timestamp manipulation, with
the intent to replace circulation of fresh packets with outdated packets in the
network. We demonstrate how network topology capacitates an adversary to
influence age scaling in a network. We show that in a fully connected network,
a single infected node increases the expected age from $O(\log n)$ to $O(n)$.
Further, we show that the optimal behavior for an adversary is to reset the
timestamps of all outgoing packets to the current time and of all incoming
packets to an outdated time for the infected node; thereby preventing any fresh
information to go into the infected node, and facilitating acceptance of stale
information out of the infected node into other network nodes. Lastly for fully
connected network, we show that if an infected node contacts only a single node
instead of all nodes of the network, the system age can still be degraded to
$O(n)$. These show that fully connected nature of a network can be both a
benefit and a detriment for information freshness; full connectivity, while
enabling fast dissemination of information, also enables fast dissipation of
adversarial inputs. We then analyze the unidirectional ring network, the other
end of the network connectivity spectrum, where we show that the adversarial
effect on age scaling of a node is limited by its distance from the adversary,
and the age scaling for a large fraction of the network continues to be
$O(\sqrt{n})$, unchanged from the case with no adversary. We finally support
our findings with simulations.
