active utility tunnels since pipes can spew boiling hot water or steam from leaky valves or pressure relief blow-offs. Often there are puddles of muddy water on the floor, making slips and falls a special concern near hot pipes. Steam tunnels have generally been secured more heavily in recent years due to their frequent use for carrying communications network backbone cables, increased safety and liability concerns, and perceived risk of use in terrorist activities. Popularity The rise in urban exploration's popularity can be attributed to increased media attention. Recent television shows such as Urban Explorers on the Discovery Channel, MTV's Fear, and the Ghost Hunting exploits of The Atlantic Paranormal Society have packaged the hobby for a popular audience. The fictional film After... (2006), a hallucinatory thriller set in Moscow's underground subways, features urban explorers caught up in extreme situations. Talks and exhibits on urban exploration have appeared at the fifth and sixth Hackers on Planet Earth Conference, complementing numerous newspaper articles and interviews. Another source of popular information is Cities of the Underworld, a documentary series that ran for three seasons on the History Channel starting in 2007. This series roamed around the world, showing little-known underground structures in remote locales and right under the feet of densely packed city-dwellers. Websites for professional and hobby explorers have been developed to share tips and locations. With the rise in the hobby's popularity, there has been increasing discussion of whether the extra attention has been beneficial. Legality The activity's growing popularity has resulted in increased attention not just from explorers but also from vandals and law enforcement. The illicit aspects of urban exploring, which may include trespassing and breaking and entering, have had critical attention in mainstream newspapers. In Australia, lawyers for the Roads and Traffic Authority of New South Wales shut down the Sydney Cave Clan's website after they raised concerns that the portal could "risk human safety and threaten the security of its infrastructure". Another website belonging to the Bangor Explorers Guild was criticized by the Maine State Police for encouraging behavior that "could get someone hurt or killed". Toronto Police, called for an "end" to rooftop photography in 2016, citing similar concerns about the possibility of death or injury.The Toronto Transit Commission has used the Internet to crimp subway tunnel explorations, going as far as to send investigators to various explorers' homes. Jeff Chapman, who authored Infiltration, writes