2019-08-26 18:33:55 H=e2e-36-163.e2enetworks.net.in [101.53.139.163]:51230 I=[192.147.25.65]:25 sender verify fail for : all relevant MX records point to non-existent hosts
2019-08-26 18:33:55 H=e2e-36-163.e2enetworks.net.in [101.53.139.163]:51230 I=[192.147.25.65]:25 F= rejected RCPT : Sender verify failed
2019-08-26 18:37:57 H=e2e-36-163.e2enetworks.net.in [101.53.139.163]:16866 I=[192.147.25.65]:25 F= rejected RCPT : RBL: found in thrukfz5b56tq6xao6odgdyjrq.zen.dq.spamhaus.net (127.0.0.4) (https://www.spamhaus.org/query/ip/101.53.139.163)
...

Splunk® : port scan detected:
Aug 26 22:25:42 testbed kernel: Firewall: *TCP_IN Blocked* IN=eth0 OUT= MAC=82:c6:52:d1:6e:53:c0:42:d0:39:2c:30:08:00 SRC=185.79.99.245 DST=104.248.11.191 LEN=40 TOS=0x00 PREC=0x00 TTL=236 ID=33281 PROTO=TCP SPT=50518 DPT=3389 WINDOW=1024 RES=0x00 SYN URGP=0

$f2bV_matches

2019-08-27T03:39:38.321410abusebot-4.cloudsearch.cf sshd\[15013\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=128.14.136.158  user=sshd

Aug 26 15:42:08 kapalua sshd\[10365\]: Invalid user oracle from 52.232.127.201
Aug 26 15:42:08 kapalua sshd\[10365\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=smtp4.ibsgen.com
Aug 26 15:42:10 kapalua sshd\[10365\]: Failed password for invalid user oracle from 52.232.127.201 port 16287 ssh2
Aug 26 15:46:37 kapalua sshd\[10851\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=smtp4.ibsgen.com  user=root
Aug 26 15:46:39 kapalua sshd\[10851\]: Failed password for root from 52.232.127.201 port 24886 ssh2

fail2ban

Aug 27 06:01:34 rpi sshd[15244]: Failed password for root from 64.76.6.126 port 59254 ssh2
Aug 27 06:08:25 rpi sshd[15428]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=64.76.6.126

Aug 27 02:38:31 MK-Soft-Root2 sshd\[910\]: Invalid user bike from 117.48.208.71 port 55244
Aug 27 02:38:31 MK-Soft-Root2 sshd\[910\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=117.48.208.71
Aug 27 02:38:33 MK-Soft-Root2 sshd\[910\]: Failed password for invalid user bike from 117.48.208.71 port 55244 ssh2
...

Aug 26 18:08:14 hanapaa sshd\[28377\]: Invalid user amavis from 139.59.59.154
Aug 26 18:08:14 hanapaa sshd\[28377\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=139.59.59.154
Aug 26 18:08:16 hanapaa sshd\[28377\]: Failed password for invalid user amavis from 139.59.59.154 port 56276 ssh2
Aug 26 18:15:24 hanapaa sshd\[29115\]: Invalid user student8 from 139.59.59.154
Aug 26 18:15:24 hanapaa sshd\[29115\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=139.59.59.154

Aug 27 03:47:04 MK-Soft-VM7 sshd\[5588\]: Invalid user hadoop from 148.70.77.122 port 41518
Aug 27 03:47:04 MK-Soft-VM7 sshd\[5588\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=148.70.77.122
Aug 27 03:47:06 MK-Soft-VM7 sshd\[5588\]: Failed password for invalid user hadoop from 148.70.77.122 port 41518 ssh2
...

Aug 27 04:42:18 yabzik sshd[4307]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=108.36.94.38
Aug 27 04:42:20 yabzik sshd[4307]: Failed password for invalid user lily from 108.36.94.38 port 9420 ssh2
Aug 27 04:46:39 yabzik sshd[5898]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=108.36.94.38

Aug 27 06:14:22 vps647732 sshd[5319]: Failed password for sshd from 173.244.209.5 port 51198 ssh2
Aug 27 06:14:36 vps647732 sshd[5319]: error: maximum authentication attempts exceeded for sshd from 173.244.209.5 port 51198 ssh2 [preauth]
...

Aug 27 06:20:39 [munged] sshd[23737]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=84.120.41.118  user=root
Aug 27 06:20:41 [munged] sshd[23737]: Failed password for root from 84.120.41.118 port 57130 ssh2

2019-08-27T02:17:42.041490abusebot-3.cloudsearch.cf sshd\[22758\]: pam_unix\(sshd:auth\): authentication failure\; logname= uid=0 euid=0 tty=ssh ruser= rhost=128.199.219.121  user=root

$f2bV_matches