Date: Fri, 8 Jun 2012 15:43:47 +0300 From: Nikolay Denev <ndenev@gmail.com> To: Adrian Chadd <adrian@FreeBSD.org> Cc: freebsd-net <freebsd-net@freebsd.org> Subject: Re: FreeBSD 8.2-STABLE sending FIN no ACK packets. Message-ID: <CBFAA2DA-D8D2-466E-83EC-D40505250270@gmail.com> In-Reply-To: <CAJ-Vmo=82Y-oD3gpNZQ_Q4UHWrRqk_Vs2QZqshGXv_E=LqY8-w@mail.gmail.com> References: <54EF0399-B36E-42CA-9526-DDC7ADA4406A@gmail.com> <CAJ-Vmo=82Y-oD3gpNZQ_Q4UHWrRqk_Vs2QZqshGXv_E=LqY8-w@mail.gmail.com>
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On Jun 8, 2012, at 4:30 AM, Adrian Chadd wrote: > On 7 June 2012 05:41, Nikolay Denev <ndenev@gmail.com> wrote: >> Hello, >>=20 >> I've been pointed out by our partner that we are sending TCP packets = with FIN flag and no ACK set, which is triggering >> alerts on their firewalls. >> I've investigated, and it appears that some of our FreeBSD hosts are = really sending such packets. (they are running some java applications) >> I did "tcpdump -s0 -vni em1 '(tcp[tcpflags] & tcp-ack =3D=3D 0) && = (tcp[tcpflags] & tcp-fin !=3D 0)'" to catch them. >>=20 >> Is this considered normal? >> It seems at least Juniper considers this malicious traffic : = http://www.juniper.net/techpubs/software/junos-security/junos-security10.0= /junos-security-swconfig-security/id-72577.html >=20 > Would you please file a PR with this, so it doesn't get lost? >=20 > Thanks, >=20 >=20 > Adrian Filed as kern/168842, and mistakenly duplicated as kern/168843 (the = latter can be closed). As I wrote in the PR, I have a PCAP that I can privately share if = someone is interested.
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