Loading skill
Install any skill in seconds. Free to start, no credit card required.
Get Started Free →Adversaries may perform calculations on addresses returned in DNS results to determine which port and IP address to use for command and control, rather than relying on a predetermined port number o...
.claude/skills/cyberstrikeus-t1568-003-dns-calculation/SKILL.md| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-01 | ✗→✓ | ▲ Improved | 79% | 0% |
| case-05 | ✗→✓ | ▲ Improved | -70% | 0% |
| case-06 | ✗→✓ | ▲ Improved | -14% | 0% |
| case-12 | ✗→✓ | ▲ Improved | -67% | 0% |
| case-14 | ✗→✓ | ▲ Improved | -26% | 0% |
> Sub-technique of: T1568
Adversaries may perform calculations on addresses returned in DNS results to determine which port and IP address to use for command and control, rather than relying on a predetermined port number or the actual returned IP address. A IP and/or port number calculation can be used to bypass egress filtering on a C2 channel.
One implementation of DNS Calculation is to take the first three octets of an IP address in a DNS response and use those values to calculate the port for command and control traffic.
Platforms: Linux, macOS, Windows, ESXi
> Note: No Atomic Red Team tests available for this technique. See Atomic Red Team GitHub for updates.
No specific mitigations documented for this technique.
| Finding | Severity | Impact | | ------------------------------------ | -------- | ------------------- | | DNS Calculation technique applicable | Low | Command And Control |
| CWE ID | Title | | ------- | ---------------------------------- | | CWE-300 | Channel Accessible by Non-Endpoint |
| Case | Status | Duration (ms) | Turns | Tokens | Tool calls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Without | With | Δ | Without | With | Δ | Without | With | Δ | Without | With | Δ | ||
case-01 | fail→pass | 26,059 | 38,454 | +48% | 1 | 1 | 0% | 3,470 | 6,195 | +79% | 0 | 0 | — |
case-02 | fail→fail | 30,870 | 33,274 | +8% | 1 | 1 | 0% | 4,868 | 5,251 | +8% | 0 | 0 | — |
case-03 | fail→fail | 31,736 | 31,902 | +1% | 1 | 1 | 0% | 3,804 | 4,813 | +27% | 0 | 0 | — |
case-04 | pass→pass | 25,713 | 44,539 | +73% | 1 | 1 | 0% | 3,988 | 7,374 | +85% | 0 | 0 | — |
case-09 | pass→pass | 20,227 | 17,439 | -14% | 1 | 1 | 0% | 2,409 | 3,023 | +25% | 0 | 0 | — |
case-05 | fail→pass | 29,963 | 4,260 | -86% | 1 | 1 | 0% | 4,421 | 1,323 | -70% | 0 | 0 | — |
case-06 | fail→pass | 7,154 | 9,675 | +35% | 1 | 1 | 0% | 1,243 | 1,069 | -14% | 0 | 0 | — |
case-07 | fail→fail | 21,780 | 28,495 | +31% | 1 | 1 | 0% | 2,904 | 4,536 | +56% | 0 | 0 | — |
case-08 | pass→pass | 11,761 | 9,690 | -18% | 1 | 1 | 0% | 2,342 | 1,600 | -32% | 0 | 0 | — |
case-10 | pass→pass | 6,006 | 8,392 | +40% | 1 | 1 | 0% | 1,066 | 1,185 | +11% | 0 | 0 | — |
case-11 | pass→pass | 10,475 | 6,759 | -35% | 1 | 1 | 0% | 1,102 | 982 | -11% | 0 | 0 | — |
case-12 | fail→pass | 21,477 | 7,402 | -66% | 1 | 1 | 0% | 3,026 | 986 | -67% | 0 | 0 | — |
case-13 | fail→fail | 19,742 | 24,184 | +23% | 1 | 1 | 0% | 2,589 | 3,430 | +32% | 0 | 0 | — |
case-14 | fail→pass | 22,015 | 6,570 | -70% | 1 | 1 | 0% | 2,488 | 1,851 | -26% | 0 | 0 | — |
case-15 | fail→pass | 14,204 | 7,123 | -50% | 1 | 1 | 0% | 1,355 | 1,054 | -22% | 0 | 0 | — |
case-16 | pass→pass | 21,135 | 6,689 | -68% | 1 | 1 | 0% | 3,692 | 991 | -73% | 0 | 0 | — |
case-17 | fail→pass | 25,723 | 23,345 | -9% | 1 | 1 | 0% | 3,602 | 3,471 | -4% | 0 | 0 | — |
case-18 | fail→pass | 23,758 | 10,238 | -57% | 1 | 1 | 0% | 3,378 | 954 | -72% | 0 | 0 | — |
case-19 | fail→pass | 23,408 | 7,286 | -69% | 1 | 1 | 0% | 2,630 | 1,072 | -59% | 0 | 0 | — |
case-20 | fail→pass | 23,342 | 17,774 | -24% | 1 | 1 | 0% | 2,836 | 2,513 | -11% | 0 | 0 | — |
case-21 | fail→pass | 21,258 | 16,340 | -23% | 1 | 1 | 0% | 2,545 | 2,530 | -1% | 0 | 0 | — |
case-22 | pass→pass | 14,106 | 14,733 | +4% | 1 | 1 | 0% | 1,459 | 2,258 | +55% | 0 | 0 | — |
case-23 | pass→pass | 12,329 | 11,453 | -7% | 1 | 1 | 0% | 1,308 | 1,589 | +21% | 0 | 0 | — |
case-24 | pass→pass | 16,584 | 16,112 | -3% | 1 | 1 | 0% | 1,906 | 2,471 | +30% | 0 | 0 | — |
DecimalAI ran this skill against gemini-3.6-flash twice over the same eval suite — once with the skill loaded and once without — and compared the two runs case by case. 24 cases were attempted. The headline lift of +46 percentage points is the difference between those two pass rates over the 24 comparable cases.
Without the skill loaded, the model failed this case. With it loaded, the same prompt on the same model passed. This is one improved case from the latest verified run; every case, including any that regressed, is in the table above.
Other measured skills in the registry, with their headline benchmark lift.