/etc/netscript/ipfilter-defs/example2.def is in netscript-2.4 5.2.9ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Rules for accessing Internet from Office and Server LAN...
#
# Access from Office to internet - only allow outgoing tcp and UDP
# and ping traffic - anything else is most like a tunneling protocol
# We have VPNs for tunneling
#ipv4_compile_chain -p 90 offcInet droplog $OFFICE_REGN $INTERNET_REGN
#offcInet ACCEPT_EST BOTH
#offcInet ACCEPT_PING L2R
#offcInet ACCEPT_TCP L2R 1:65535
#offcInet ACCEPT_UDP L2R 1:65535
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