All three of Octel's servers would become unresponsive for no apparent reason. Sometimes they crashed after a while but sometimes they would come back up after a while.
Late one night when no one else was there I ran "top" only to puzzle over that a bunch of identical command lines were consuming all the CPU:
login -p Mkkuow....
I don't remember the exact username but this Mkkuow guy was trying to log into all the terminals on each box.
I dont clearly recall how I figured this out but it was the result of capacitive coupling - parasitic capacitance - between the transmit and receive rs232 wires. The OS would transmit "SunOS login:" then get garbage on the receive line. Then it would prompt for the password a few times, eventually to give up and transmit the login prompt again.
The actual username I saw is easy to figure out by graphing the ASCII voltage levels then considering how capacitance works.
The solution was to replace all the cables with a lower capacitance cable. Because that required all new connectors as well as my time to install them my manager Karen Coates required some convincing but in the end the new cable stopped the hangs.
Late one night when no one else was there I ran "top" only to puzzle over that a bunch of identical command lines were consuming all the CPU:
I don't remember the exact username but this Mkkuow guy was trying to log into all the terminals on each box.I dont clearly recall how I figured this out but it was the result of capacitive coupling - parasitic capacitance - between the transmit and receive rs232 wires. The OS would transmit "SunOS login:" then get garbage on the receive line. Then it would prompt for the password a few times, eventually to give up and transmit the login prompt again.
The actual username I saw is easy to figure out by graphing the ASCII voltage levels then considering how capacitance works.
The solution was to replace all the cables with a lower capacitance cable. Because that required all new connectors as well as my time to install them my manager Karen Coates required some convincing but in the end the new cable stopped the hangs.