TSUBAME Report Overflow (Oct-Dec 2021)

This TSUBAME Report Overflow series discuss monitoring trends of overseas TSUBAME sensors and other activities which the Internet Threat Monitoring Quarterly Reports does not include. This article covers the monitoring results for the period of October to December 2021. The scan trends observed with TSUBAME sensors in Japan are presented in graphs here.

Scan packets to GRE increased

Table 1 shows the top 5 packets sent from IP addresses in Japan, which the Internet Threat Monitoring Quarterly Report did not cover. Packets to Generic Routing Encapsulation (GRE) were observed the most. These packets were observed by a wide range of sensors.

Table 1: Top 5 protocols/port numbers of TSUBAME sensors in Japan that observed packets the most

Rank Protocols/Port numbers
1 GRE
2 23/TCP
3 445/TCP
4 37215/TCP
5 8545/TCP

GRE is a tunneling protocol that transmits encapsulated data through GRE tunnels. The result of the packet captures that TSUBAME sensors observed are shown in Figure 1 although it is not clear whether they are meaningful. (Some information about TSUBAME sensor is masked.)

Figure 1: Sample of observed GRE packets

We checked the sources of GRE packets using data from scan data service providers such as SHODAN and Censys, but we found nothing in common such as specific operating systems or software running. However, we confirmed that web servers and IoT products such as surveillance cameras and recorders were running at some of the senders. As a part of our incident response, JPCERT/CC is notifying the administrators of those IP addresses in Japan which sent GRE packets.

Comparison of the observation trends in Japan and overseas

Figures 2 and 3 show a monthly comparison of the daily average number of packets received by a single sensor in Japan and overseas. More packets were observed in the overseas sensors than in the domestic sensors. You can also see that more packets were observed by sensors both in Japan and abroad in every month compared to the same months in the previous year.

Figure 2: Average number of packets to domestic sensors Figure 3: Average number of packets to overseas sensors

Comparison of monitoring trends by sensor

A global IP address is assigned to each TSUBAME sensor. Table 2 shows the top 10 ports of each sensor which received packets the most. 6379/TCP, 23/TCP, 22/TCP, etc., which Redis uses, were observed by all sensors. There is no significant difference in observation results between sensors in Japan and overseas while the order of ports is slightly different. This suggests that these protocols are being scanned in a wide range of networks.

Table 2: Comparison of top 10 packets by domestic and overseas sensors

  #1 #2 #3 #4 #5 #6 #7 #8 #9 #10
Domestic sensor1 123/UDP 6379/TCP 5555/TCP 23/TCP 22/TCP 445/TCP ICMP 2375/TCP 443/TCP 80/TCP
Domestic sensor2 6379/TCP 23/TCP 123/UDP 22/TCP 445/TCP 443/TCP 2375/TCP 80/TCP 2376/TCP 1433/TCP
Domestic sensor3 6379/TCP 23/TCP 22/TCP 445/TCP 443/TCP 37215/TCP 80/TCP 5060/UDP 2375/TCP 1433/TCP
Overseas sensor1 6379/TCP 23/TCP 22/TCP 5060/UDP 80/TCP 5555/TCP 1433/TCP 443/TCP GRE 81/TCP
Overseas sensor2 23/TCP 6379/TCP 445/TCP 22/TCP 139/TCP 1433/TCP 5060/UDP 80/TCP 443/TCP 5555/TCP
Overseas sensor3 445/TCP 139/TCP 6379/TCP 23/TCP 22/TCP 123/UDP 5555/TCP ICMP 5060/UDP 2375/TCP

In closing

Monitoring at multiple points makes it possible to see whether some trends are unique to a particular network. We observed scan packets for Redis both in Japan and other regions, and we are preparing to provide information to CSIRTs of those regions, hoping that we can make some changes. As for GRE, there is no public information addressing this issue at this point. We will figure out this trend based on the information in the feedback we receive. In this quarter, we did not publish any special security alert or other information, but the attention should be paid to the above issue regarding Redis when using the Internet. We will continue to publish blog articles as the Internet Threat Monitoring Quarterly Report becomes available every quarter. We will also publish an extra issue when we observe any unusual change. Your feedback on this series is much appreciated. Please use the below comment form to let us know which topic you would like us to introduce or discuss further. Thank you for reading.

Keisuke Shikano (Translated by Takumi Nakano)

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