Sonic1: Mirai Variant Targeting Multiple Vulnerabilities
- Sonic1 is a Mirai-derived botnet variant that exploits multiple vulnerabilities (e.g., SonicWall SSL-VPN, D-Link, Yealink) to compromise enterprise and IoT devices.
- It employs automated scanning, command injection, and payload staging via shell scripts (lolol.sh, install.sh) to propagate using both exploit-driven and SSH brute-force methods.
- Defensive insights emphasize timely patching, robust input validation, and strict credential management to mitigate the broad exploit surface used by Sonic1.
Sonic1 denotes a Mirai-derived IoT botnet variant discussed under the shorter label Sonic in “Analyzing The Mirai IoT Botnet and Its Recent Variants: Satori, Mukashi, Moobot, and Sonic” (Famera et al., 3 Aug 2025). In that account, Sonic is an unnamed Mirai variant observed in February 2021 and unofficially named by the authors because one of its key targets is a SonicWall SSL-VPN vulnerability. Its significance lies less in quantified botnet scale than in its exploit breadth: the variant is described as targeting six recently discovered vulnerabilities across multiple vendors, alongside three additional unidentified command-injection vulnerabilities, with the introduction further stating that it “continues to utilize three zero-day vulnerabilities” (Famera et al., 3 Aug 2025). A plausible implication is that the label “Sonic1” is a later naming convenience for the same botnet that the paper calls Sonic.
1. Designation, discovery, and placement within the Mirai lineage
Sonic1 is treated as one of four “recent” Mirai variants, together with Satori, Mukashi, and Moobot (Famera et al., 3 Aug 2025). The paper states that there was no official name for the botnet at the time of writing, and that the designation Sonic was adopted because of its exploitation of a SonicWall SSL-VPN flaw. Figure 1 in the paper marks the timeline entry “Feb 12. Unit42 Researchers observe Sonic Botnet.” (Famera et al., 3 Aug 2025)
Within the paper’s taxonomy, Sonic is not presented as a wholly novel malware family, but as a Mirai variant that preserves Mirai-like propagation characteristics while updating its exploit surface toward newer enterprise, networking, and IoT targets (Famera et al., 3 Aug 2025). This positioning is important. The article repeatedly frames Sonic as a member of a lineage whose distinguishing properties are automated scanning, propagation, compromise of Internet-exposed devices, and deployment of Mirai-derived binaries. Sonic’s distinctiveness is therefore not its basic architecture, but its exploit portfolio and recency.
The paper emphasizes that Sonic is notable for multiple recent and unknown vulnerabilities, rather than for a documented Sonic-specific bot population or a quantified operational campaign. This matters interpretively: the evidence base for Sonic in the paper is strongest on compromise mechanics and post-exploitation tooling, but comparatively weak on command-and-control telemetry and botnet-scale measurement (Famera et al., 3 Aug 2025).
2. Exploit surface and targeted vulnerabilities
The Sonic section and Table III associate the variant with a heterogeneous set of vulnerabilities affecting security appliances, network-attached storage, device-management software, routers, switches, and embedded firmware (Famera et al., 3 Aug 2025). The paper presents this exploit set as distinct from those of Satori, Mukashi, and Moobot.
| Target | Identifier | Weakness or access condition |
|---|---|---|
| SonicWall SSL-VPN | N/A | “VPN Exploit”; unauthenticated remote code execution via old Bash vulnerable to ShellShock |
| D-Link DNS-320 Revision Ax | CVE-2020-25506 | OS command injection |
| Yealink Device Management 3.6.0.20 | CVE-2021-27561 | Command injection |
| Arm Trusted Firmware-M through 1.2 | CVE-2021-27562 | Out-of-bounds write |
| Micro Focus Operation Bridge Reporter 10.40 | CVE-2021-22502 | Code injection |
| Netis WF2419 | CVE-2019-19356 | OS command injection / authenticated RCE |
| NETGEAR JGS516PE | CVE-2020-26919 | Lack of access control at the function level |
| Unspecified products | Unknown | Three unidentified command-injection vulnerabilities |
The vulnerability most closely tied to the botnet’s naming is the VisualDoor SonicWall Secure Socket Layer VPN Command Injection affecting SonicWall SSL-VPN, exposed through /cgi-bin/jarrewrite.sh. The text describes this as unauthenticated remote code execution via an old Bash version vulnerable to ShellShock, with command execution as the “nobody” user (Famera et al., 3 Aug 2025).
The D-Link path centers on CVE-2020-25506 in D-Link DNS-320 Revision Ax, specifically system_mgr.cgi, where arbitrary command execution is attributed to improper sanitization of HTTP parameters, notably f_ntp_server. The Yealink path uses CVE-2021-27561, associated with /sm/api/v1/firewall/zone/services, and is described as allowing command execution as root without requiring any authentication. The Micro Focus path uses CVE-2021-22502, tied to improper sanitization of the username parameter in the LogonResource endpoint, yielding remote code execution. The Netis path uses CVE-2019-19356 through the tracert diagnostic tool in the router web management page, with authenticated command execution as root. The Netgear path uses CVE-2020-26919, which the paper characterizes as enabling unauthenticated attackers to execute arbitrary code through missing function-level access control. The Arm case, CVE-2021-27562, is included in Sonic’s targeted set, but the paper explicitly does not explain how the botnet operationalizes that bug during propagation (Famera et al., 3 Aug 2025).
A further complication is the paper’s assertion that Sonic also uses three unknown vulnerabilities, all described only as some type of command injection. No CVEs, product names, packet traces, or exploit strings are supplied for these. This lack of specificity is one reason Sonic is presented as technically concerning yet still somewhat opaque (Famera et al., 3 Aug 2025).
3. Infection chain and propagation workflow
Although the paper does not provide a Sonic-exclusive sequence diagram, it describes a compromise chain that combines Mirai’s baseline propagation model with Sonic-specific exploitation and downloader stages (Famera et al., 3 Aug 2025). The workflow begins with Internet-facing target acquisition. The paper states that Mirai variants, including Sonic, exhibit scanning and propagation, and generalizes in its conclusion that these variants pseudorandomly search for open ports and use brute-force attacks with common usernames and passwords. For Sonic specifically, the presence of Zmap and an SSH brute forcer in its post-exploitation toolkit supports automated large-scale discovery and credential attacks (Famera et al., 3 Aug 2025).
Exploitation terminates in command execution sufficient to invoke a downloader. The paper explicitly states that upon successful exploitation, Sonic uses wget to download a malicious shell script (Famera et al., 3 Aug 2025). The exploit surfaces named in the text are web-management, VPN, or management-API endpoints, and in the Netis case an authenticated administrative diagnostic interface. For some paths, the paper provides exact endpoints or parameters, but it does not provide raw exploit syntax or HTTP request bodies.
After the initial exploit, the botnet downloads shell-scripted staging components. The paper identifies lolol.sh and install.sh as concrete artifacts, along with nbrute and combo.txt (Famera et al., 3 Aug 2025). The staging scripts then execute several Mirai binaries one by one. These binaries are described as “dark binaries” based on the Mirai codebase and stored under the filename nginx for evasion.
The propagation logic is dual-track. Sonic is both an exploit-driven worm and a credential-abuse botnet. According to the paper, the dark binaries propagate either through the named exploits or through brute-forced SSH connections using hard-coded credentials. The file combo.txt contains commonly used credentials, while nbrute uses that file to brute-force SSH connections with IP addresses. The script install.sh downloads GoLang v1.9.4, the Go standard SSH package, and Zmap (Famera et al., 3 Aug 2025).
This attack model differs in emphasis from classic Mirai as summarized in the same paper. Original Mirai is described there primarily as abusing Telnet on ports 23/2323, whereas Sonic is characterized by a mixture of web and VPN RCE/command injection exploitation and SSH brute forcing (Famera et al., 3 Aug 2025). That shift broadens the accessible victim class from consumer IoT devices to a wider management-plane attack surface.
4. Host modification, concealment, and attempted persistence
The paper attributes several post-exploitation functions specifically to lolol.sh (Famera et al., 3 Aug 2025). It is said to delete key folders on the compromised host that are responsible for scheduling jobs and starting up processes. It downloads the Mirai-derived dark binaries, saves them under the name nginx, and implements packet filters that block incoming traffic on commonly used SSH, HTTP, Telnet, and similar ports.
These behaviors imply a takeover strategy oriented toward interference as much as persistence. Blocking common management ports can impede administrator access and may also reduce competition from other malware families. Naming the binary nginx suggests a basic masquerading tactic, using a common process or file name to blend into expected system contents. The deletion or tampering of scheduling- and startup-related folders suggests an attempt to alter local execution conditions beyond mere transient compromise (Famera et al., 3 Aug 2025).
Persistence, however, is presented cautiously. The paper states that lolol.sh is “supposed to be rerun every hour,” but also reports that “the cron command-line utility is said to be improperly configured” (Famera et al., 3 Aug 2025). The implication is not robust persistence, but rather an attempted cron-based persistence mechanism whose correctness is doubtful. This is one of the few concrete operational limitations attributed to Sonic in the paper.
The combination of packet filtering, downloader staging, masqueraded binary placement, and partial persistence makes Sonic resemble a lightweight operational platform rather than a single-shot exploit script. Yet the paper does not present artifact hashes, filesystem forensics, or process-lifecycle telemetry in sufficient detail to elevate those observations into a complete implant model (Famera et al., 3 Aug 2025).
5. Command-and-control, capabilities, and evidentiary limits
Sonic is described as a Mirai variant, so its inclusion in a C&C-controlled botnet lineage is explicit at the family level (Famera et al., 3 Aug 2025). The downloaded binaries are based on the Mirai codebase, and the scripts are clearly designed to spread malware and operationalize the botnet. Beyond that, the paper is notably sparse on Sonic-specific command-and-control telemetry. It provides no Sonic-specific C2 IP addresses, no Sonic-specific TCP/UDP C2 ports, no protocol message formats, and no command taxonomy comparable to the much richer C2 treatment given for Mukashi (Famera et al., 3 Aug 2025).
This evidentiary asymmetry is important for avoiding overstatement. The paper supports the existence of a Mirai-style control plane by family resemblance, but not a concrete reconstruction of Sonic’s C2 infrastructure. Likewise, the botnet’s objectives are clearest in terms of infection and propagation, not a documented Sonic-only attack catalog. The paper states that, as a Mirai variant, Sonic sits in a family used for DDoS attacks, but it does not present a measured Sonic-specific DDoS campaign, volumetric event, or operational trace (Famera et al., 3 Aug 2025).
A similar limitation applies to scale. The article provides no exact Sonic bot count, no infection-speed metric, no regional distribution, no scanning volume, and no success-rate estimate (Famera et al., 3 Aug 2025). It does provide quantitative context for other variants—such as Satori’s early growth and Moobot’s DDoS reporting—but those figures are explicitly not Sonic-specific. The technical significance assigned to Sonic therefore derives from breadth of attack surface, downloader-based propagation, SSH credential abuse, and use of unidentified vulnerabilities, rather than from a measured prevalence claim.
This evidentiary profile can lead to a common misunderstanding: that Sonic is important because its scale has been directly quantified. The paper supports the opposite conclusion. Sonic is important in the article because it is exploit-rich and recency-heavy, while its operational size remains underdescribed (Famera et al., 3 Aug 2025).
6. Defensive implications and analytical interpretation
The paper’s defense discussion is framed at the Mirai-family level, but several recommendations map directly onto Sonic’s attack paths (Famera et al., 3 Aug 2025). The most immediate is patch and update management for exposed devices and services, since Sonic targets known vulnerabilities in SonicWall SSL-VPN, D-Link DNS-320, Yealink Device Management, Arm Trusted Firmware-M, Micro Focus Operation Bridge Reporter, Netis WF2419, and NETGEAR JGS516PE. The article recommends periodically updating firmware and applications and, more generally, designing devices for automatic firmware/OS updates.
A second direct implication concerns input validation. Several Sonic-linked exploits are explicitly described as arising from improper sanitization or injection flaws, including the D-Link f_ntp_server parameter, the Micro Focus username parameter, and the Yealink command-injection endpoint. The paper therefore recommends proper constraint validation, since many of the relevant vulnerabilities arise from injection attacks (Famera et al., 3 Aug 2025).
A third implication concerns credential hygiene. Sonic uses brute-forced SSH connections using hard-coded credentials, with combo.txt storing common usernames and passwords and nbrute applying them against target IPs. The paper recommends changing default credentials, adopting more complex and unique credentials, and having manufacturers randomize usernames and passwords (Famera et al., 3 Aug 2025).
Exposure management is also central. Although the paper’s generic examples emphasize Telnet ports 23/2323, the same logic extends directly to Sonic’s web-management, SSH, and SSL-VPN surfaces. The article recommends securing networks with VPNs, a separate network, and firewall/IDS/IPS deployments, as well as closing/stopping nonessential services and leaving devices offline if not used for long periods (Famera et al., 3 Aug 2025). A plausible implication is that limiting Internet exposure of administrative CGI endpoints, router/switch web management, device-management APIs, and SSH materially reduces Sonic’s reachable attack surface.
Finally, the paper notes that botnets often have difficulty maintaining control once an infected device is rebooted, especially if the underlying vulnerability is then patched (Famera et al., 3 Aug 2025). In Sonic’s case, this observation is especially pertinent because the paper describes its cron-style rerun mechanism as improperly configured. This suggests that Sonic’s persistence may be brittle on at least some targets, though the paper does not convert that into a universal remediation guarantee.
Taken together, Sonic1 emerges as an exploit-oriented Mirai variant whose analytic significance lies in compromise methodology rather than fully disclosed operations. It is best understood as a Mirai-style propagation engine updated for newer enterprise, networking, and IoT attack surfaces, with a workflow centered on web/VPN exploitation, shell-scripted payload delivery, SSH brute force, and Mirai-derived binary deployment (Famera et al., 3 Aug 2025). The article’s strongest conclusion is therefore not that Sonic’s scale has been measured, but that a contemporary Mirai descendant can combine known high-severity flaws, unknown command injections, and lightweight post-exploitation tooling into a broad, adaptable infection platform.