The Register reports on a recent discovery linking Iran to the Ansar al-Mujahideen Forum.
The article is here
and the excel file and a description can be found here
See the Register article (above) and this wikipedia page for discussion of X.25
My layman's understanding is that this is essentially a dedicated data line, such as one might have for an office. And in Iran, those lines are approved and controlled the government telco, DCI. The data suggests the activity occurred in the northeast of Iran, adjoining Afghanistan.