The anti-pornography internet filter recently implemented by UK's top internet service providers is blocking League of Legends updates after discovering the letters s-e-x in its files.
To be more precise, the following files are being blocked by the filter, forcing the update to fail with a "file not found" error.:
XerathMageChainsExtended.luaobj
VarusExpirationTimer.luaobj
In case you couldn't find it yet, here is the sex in those files:
XerathMageChainsExtended.luaobj
VarusExpirationTimer.luaobj
British internet users have had the option enable pornography filters for their internet connections. By the end of 2013, the country's top ISPs agreed to enable those filters by default to all new customers and give them the option to disable it.