Ubuntu – What could be the cause for these strange UFW block entries in the syslog

firewallsyslogufw

I've recently noticed a large number of recurring UFW blocks in my syslog. This surprised me as I have no UFW rules set:

$ sudo ufw status verbose
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing)
New profiles: skip

Could someone more versed with firewall configurations on Ubuntu/Linux please tell me why I am getting these entries?

Apr  7 20:01:04 mhcUBN kernel: [18234.747861] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3586 DF PROTO=2 
Apr  7 20:03:09 mhcUBN kernel: [18359.541595] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3587 DF PROTO=2 
Apr  7 20:05:14 mhcUBN kernel: [18484.335607] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3588 DF PROTO=2 
Apr  7 20:07:19 mhcUBN kernel: [18609.129970] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3589 DF PROTO=2 
Apr  7 20:09:24 mhcUBN kernel: [18733.923467] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3590 DF PROTO=2 
Apr  7 20:10:01 mhcUBN CRON[31522]: (mhc) CMD ("/home/mhc/.scripts/Customization/Powersaving/battmonitor")
Apr  7 20:11:29 mhcUBN kernel: [18858.717504] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3591 DF PROTO=2 
Apr  7 20:13:34 mhcUBN kernel: [18983.510575] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3592 DF PROTO=2 
Apr  7 20:15:39 mhcUBN kernel: [19108.306349] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3593 DF PROTO=2 
Apr  7 20:17:01 mhcUBN CRON[582]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Apr  7 20:17:44 mhcUBN kernel: [19233.100675] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3594 DF PROTO=2 
Apr  7 20:19:49 mhcUBN kernel: [19357.893801] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3595 DF PROTO=2 
Apr  7 20:20:01 mhcUBN CRON[1272]: (mhc) CMD ("/home/mhc/.scripts/Customization/Powersaving/battmonitor")
Apr  7 20:21:54 mhcUBN kernel: [19482.686449] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3596 DF PROTO=2 
Apr  7 20:23:59 mhcUBN kernel: [19607.480499] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3597 DF PROTO=2 
Apr  7 20:26:04 mhcUBN kernel: [19732.274979] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3598 DF PROTO=2 
Apr  7 20:28:09 mhcUBN kernel: [19857.068910] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3599 DF PROTO=2 
Apr  7 20:30:01 mhcUBN CRON[3484]: (mhc) CMD ("/home/mhc/.scripts/Customization/Powersaving/battmonitor")
Apr  7 20:30:14 mhcUBN kernel: [19981.862231] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3600 DF PROTO=2 
Apr  7 20:32:19 mhcUBN kernel: [20106.657165] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3601 DF PROTO=2 
Apr  7 20:34:24 mhcUBN kernel: [20231.450561] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3602 DF PROTO=2 
Apr  7 20:36:29 mhcUBN kernel: [20356.244475] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3603 DF PROTO=2 
Apr  7 20:38:34 mhcUBN kernel: [20481.038479] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3604 DF PROTO=2 
Apr  7 20:40:01 mhcUBN CRON[5702]: (mhc) CMD ("/home/mhc/.scripts/Customization/Powersaving/battmonitor")
Apr  7 20:40:39 mhcUBN kernel: [20605.832618] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3605 DF PROTO=2 
Apr  7 20:42:44 mhcUBN kernel: [20730.626727] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3606 DF PROTO=2 
Apr  7 20:44:49 mhcUBN kernel: [20855.419706] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3607 DF PROTO=2 
Apr  7 20:46:54 mhcUBN kernel: [20980.214309] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3608 DF PROTO=2 
Apr  7 20:48:59 mhcUBN kernel: [21105.008870] [UFW BLOCK] IN=eth0 OUT= MAC=01:00:5e:00:00:01:00:04:0e:ef:71:fe:08:00 SRC=192.168.178.1 DST=224.0.0.1 LEN=36 TOS=0x00 PREC=0xC0 TTL=1 ID=3609 DF PROTO=2

I have found these threads which point to a multicast problem:

http://ubuntuforums.org/showthread.php?t=1886913

https://bbs.archlinux.org/viewtopic.php?id=142525

https://issues.apache.org/jira/browse/TS-775

I am no network expert by any means and don't properly understand what is actually going on. If anyone "translated" these so that I comprehend what's going on, I'd be very happy.

Best Answer

I believe you have some service on your local network that is advertising itself or looking for clients. It's your "default deny incoming" rule that's blocking this traffic. Yours looks much like persistent noise I see on my home network, caused by a Multicast DNS server in my router.

mDNS multicasts to 224.0.0.251, so that's not what yours is. You have something multicasting to 224.0.0.1, a generic "all hosts" address. Couldn't tell you what it is from that, but from the subnet address (x.x.x.1) I'm guessing your router is the source.

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