Virtual Local Area Networks (VLANs) should not be counted on as a security feature of modern managed Ethernet switch networks. This is now common knowledge, both in IT departments and also in the Industrial Control Community. Indeed in Eric Byres’ article Why VLAN Security isn't SCADA Security at all he points out that switches with VLANS are not firewalls. But are VLANs the boogeyman of industrial control system security...or are they underestimated helpers? This article examines that question in detail.