Fortinet 100 10 , Network Intrusion Detection System (NIDS) ................................................... 221

Contents
10 Fortinet Inc.
Configuring L2TP............................................... ............................................................. 213
Configuring the FortiGate unit as a L2TP gateway.................. ................................... 214
Configuring a Windows 2000 client for L2TP.............................................. ................ 217
Configuring a Windows XP client for L2TP................. ................................................ 218
Network Intrusion Detection System (NIDS) ................................................... 221
Detecting attacks ............................................................................................................ 221
Selecting the interfaces to monitor.............................................................................. 222
Disabling the NIDS............................................................................................. ......... 222
Configuring checksum verification .............................................................................. 222
Viewing the signature list ............................................................................................ 223
Viewing attack descriptions...................................................................................... ... 223
Enabling and disabling NIDS attack signatures.................... ...................................... 224
Adding user-defined signatures .................................................................................. 224
Preventing attacks .......................................................................................................... 225
Enabling NIDS attack prevention............ .................................................................... 225
Enabling NIDS attack prevention signatures .............................................................. 226
Setting signature threshold values..................................................................... ......... 226
Configuring synflood signature values........................ ................................................ 228
Logging attacks............................................................................ ................................... 228
Logging attack messages to the attack log........................................... ...................... 228
Reducing the number of NIDS attack log and email messages.................................. 229
Antivirus protection........................................................................................... 231
General configuration steps............................................... ............................................. 231
Antivirus scanning........................................................................... ................................ 232
File blocking................................................ .................................................................... 233
Blocking files in firewall traffic ..................................................................................... 233
Adding file patterns to block.................................................. ...................................... 233
Blocking oversized files and emails................ ................................................................ 234
Configuring limits for oversized files and email.................................................. ......... 234
Exempting fragmented email from blocking.................................................................... 234
Viewing the virus list ....................................................................................................... 234
Web filtering ....................................................................................................... 235
General configuration steps............................................... ............................................. 235
Content blocking............ ................................................................................................. 236
Adding words and phrases to the banned word list .................................................... 236
URL blocking................................................................................................................ ... 237
Using the FortiGate web filter ..................................................................................... 237
Using the Cerberian web filter............................................................................... ...... 240
Script filtering........ .......................................................................................................... 242
Enabling the script filter...................................................................................... ......... 242
Selecting script filter options ....................................................................................... 242