TechJury logged 1.9 million Linux-threat detections in 2022; Trend Micro clocks a 62 % jump in ransomware aimed at Penguin farms. The moral: the attacker is already compiling for your kernel. Below is a vendor-neutral, budget-tested kit that lets a 20-person SOC hunt webshells, BPF rootkits and ransomware without a single enterprise licence—and without learning C.
1. The Three Attack Patterns That Actually Hit
- Webshell via log4j-style RCE – still #1 initial access
- BPF bytecode backdoor – hides from
ps,netstat, evenlsmod - Ransomware + kernel-driver rootkit – one binary drops signed
.ko, disables IMA, encrypts/
2. Open-Source Stack That Survived Court
| Layer | Tool | Function | 2025 Admission |
|---|---|---|---|
| Image | osacquire-linux (BSD-3) |
live dd + SHA-3 | Neb. Dist. Ct. 2025-CR-112 |
| Timeline | plaso + timesketch |
30-day GUI timeline | S.D.N.Y. Master File |
| BPF Hunt | bpftool-bash (MIT) |
dumps prog IDs + maps | Mumbai Sessions 2025/1 |
| Rootkit | rkhunter-ng (GPL) |
IMA + kmod sig check | Fla. 2d DCA 2025-AP-127 |
| Report | forensic-pdf (Apache-2.0) |
signed PDF/A-2b | Fed. Ct. Naples 2025-17 |
3. Fast Deploy – Single ISO
bash
wget https://github.com/linux-ir-2025/survival-kit/releases/download/v1.0/survival.iso
# dd to USB, boot any x86_64 box, choose “Live IR”ISO contains every tool above + YARA ruleset (see #5).
4. BPF Hunt – Because ps Lies
New trend: attacker loads BPF prog attached to cgroup/connect4; socket never appears in netstat.
One-liner:
bash
bpftool prog list | awk '$2=="cgroup/connect4"{print $1}' | xargs -I{} bpftool prog dump id {}If output > 0 lines → instant IOC.
5. YARA Rules – Community Curated, Zero False Positives
| Rule | Coverage | FP Rate | Source |
|---|---|---|---|
webshell_php_b374k.yar |
1 200 hits | 0 % | github.com/Yara-Rules |
bpf_backdoor_generic.yar |
14 hits | 0 % | SANS FOR577 alumni |
ransom_ko_sig.yar |
89 hits | 0 % | Florian Roth repo |
Clone: git clone https://github.com/Yara-Rules/rules
Scan: yara -r rules/ /media/$(hostname)-$(date +%F)
6. Cost Reality Check – 12-Month, 60 Incident Budget
| Item | USD |
|---|---|
| 1 × Dell R630 (128 GB) refurbed | 1 800 |
| 4 × 4 TB SSD (RAID-5) | 1 200 |
| Electricity (24/7 @ 0.12 kWh) | 850 |
| Total | < $4 k yr⁻¹ |
| Per-case amortised | $67 |
7. Hands-On Lab – Tonight if You Want
a) Spin up survival.iso in a VM
b) Download webshell_php_b374k sample (MalwareBazaar)
c) Run plaso against /var/log – find the shell drop time
d) Use bpftool hunt – confirm no BPF backdoor
e) Export timeline + YARA hits → PDF/A-2b → case closed
8. Common Kill-Shots – Don’t Waste the Evening
- SELinux disabled? treat as IOC (most live images leave it on)
- IMA disabled? rootkit can replace kernel modules; note in timeline
- Unsigned .ko? instant red flag;
rk hunter-ngflags it automatically
Bottom Line
Linux is no longer the “set and forget” server in the corner—it’s the primary target. The ISO above gives you a court-admissible, budget-friendly way to hunt webshells, BPF ghosts and kernel-level ransomware without learning C or buying a support contract. Burn it to USB, boot the box, and you can start the incident before the pizza arrives—no invoice, no licence keys, no excuses.
