Total surface brightness in the 2 − 10 keV band for the 33 obsid s of the XMM-CDFS, after excluding the positions around the 30 brightest sources. The increase in background intensity between 2002 and 2008 is evident. The obsids are numbered from 1 to 33 according to observation date; the vertical dotted line marks the separation between the 2001 − 2002 and 2008 − 2010 observations. Filled triangles: PN; filled circles: MOS1. The MOS2 camera has values very similar to the MOS1.