File size: 2,648 Bytes
da27866 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | //! Behaviour Vector Engine.
//!
//! Raw events are folded into a compact per-process vector that decays over
//! time. Raw events themselves are short-lived; the vector is what persists.
use crate::event::EventKind;
/// Half-life of behavioural memory (simulated ms).
const HALF_LIFE_MS: f32 = 60_000.0;
#[derive(Clone, Copy, Debug, Default)]
pub struct BehaviorVector {
pub network: f32,
pub filesystem: f32,
pub memory: f32,
pub privilege: f32,
pub injection: f32,
pub persistence: f32,
}
impl BehaviorVector {
/// Exponential decay toward zero.
pub fn decay(&mut self, dt_ms: u64) {
let f = 0.5f32.powf(dt_ms as f32 / HALF_LIFE_MS);
self.network *= f;
self.filesystem *= f;
self.memory *= f;
self.privilege *= f;
self.injection *= f;
self.persistence *= f;
}
/// Fold one event into the vector.
pub fn apply(&mut self, kind: EventKind) {
use EventKind::*;
match kind {
NetworkConnect => self.network += 1.0,
FileWrite => self.filesystem += 1.0,
RwxAlloc => self.memory += 3.0,
UnsignedModuleLoad => self.memory += 2.0,
PrivilegeEscalation => self.privilege += 3.0,
CredentialAccess => self.privilege += 4.0,
RemoteThreadInjection => self.injection += 4.0,
PersistenceWrite => self.persistence += 3.0,
TempExecution => self.filesystem += 2.0,
DeletedExecutable => self.memory += 2.0,
_ => {}
}
}
/// Rough single-number summary (used only for display).
pub fn magnitude(&self) -> f32 {
(self.network.powi(2)
+ self.filesystem.powi(2)
+ self.memory.powi(2)
+ self.privilege.powi(2)
+ self.injection.powi(2)
+ self.persistence.powi(2))
.sqrt()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn decay_halves_after_half_life() {
let mut v = BehaviorVector::default();
v.apply(EventKind::NetworkConnect);
v.apply(EventKind::NetworkConnect);
assert!((v.network - 2.0).abs() < 1e-6);
v.decay(60_000);
assert!((v.network - 1.0).abs() < 1e-3);
}
#[test]
fn injection_weighs_more_than_file_io() {
let mut a = BehaviorVector::default();
let mut b = BehaviorVector::default();
a.apply(EventKind::RemoteThreadInjection);
b.apply(EventKind::FileWrite);
assert!(a.magnitude() > b.magnitude());
}
}
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