Malware-Scanner

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Malware-Scanner

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This complete implementation represents a fully featured and fault-tolerant version of a malware scanner.

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# Malware Scanner

This repository contains the complete supplementary package for the malware-scanner study in the [Algorithms](https://www.mdpi.com/1999-4893/18/12/742) journal. The archive includes three Python implementations that reflect the evolution of the scanner across the stages described in the article. The <i>Minimal Malware scanner.py</i> file shows the core Aho-Corasick automaton with a direct construction path and a simple pattern-match procedure, and serves as a didactic reference for readers who wish to observe the essential behavior of the automaton with no auxiliary components. The <i>Intermediary Malware scanner.py</i> file introduces input checks, signature normalization, and clear state-transition output that exposes the internal mechanics of the automaton. The <i>Complete Malware scanner.py</i> file provides the full version of the scanner with robust input validation, consistent failure-output propagation, and diagnostic messages that trace valid and invalid patterns; this version reflects the model used in the article. The <i>main.db</i> file is the signature database required by all three implementations, with each entry expressed in the format <i>name=hex_pattern</i>.

The <i>algorithms-18-00742.pdf</i> file provides the published article for reference, and the <i>screenshot.png</i> file offers a visual example of the automaton structure shown in <i>Appendix A</i>. This repository thus provides a transparent and reproducible supplement that demonstrates the link between the theoretical structure of the Aho-Corasick automaton and its role in a practical malware-signature scanner.

***

> **Note:** This project is part of a complementary toolkit.  
> You may also want to check out:  
> - [Optimized HEX Signature Scanner](https://github.com/Gagniuc/Aho-Corasick-Native-Malware-Scanner)  
> - [Hexadecimal Signature Extractor for Aho-Corasick](https://github.com/Gagniuc/Hexadecimal-Signature-Extractor-for-Aho-Corasick)

## Native implementation in Python

```python

import os
import re
import tkinter as t
from tkinter import filedialog as f, scrolledtext as s, ttk as k, messagebox as m
import time

# =========================
# Aho–Corasick structures
# =========================
class N:
    def __init__(a):
        a.c = {}
        a.o = []
        a.f = None

def b(p):
    r = N()
    for q in p:
        n = r
        for x in q:
            if x not in n.c:
                n.c[x] = N()
            n = n.c[x]
        n.o.append(q)
    return r

def a(y, r):
    z = []
    n = r
    for i, x in enumerate(y):
        while x not in n.c and n != r:
            n = n.f
        if x in n.c:
            n = n.c[x]
        for q in n.o:
            z.append((i - len(q) + 1, q))
    return z

def d(r):
    q = []
    for n in r.c.values():
        n.f = r
        q.append(n)
    while q:
        g = q.pop(0)
        for x, s in g.c.items():
            q.append(s)
            f_ = g.f
            while x not in f_.c and f_ != r:
                f_ = f_.f
            s.f = f_.c.get(x, r)
            s.o += s.f.o  # inherit outputs from failure links

# =========================
# Signature loading & validation
# =========================
def is_valid_token(tok):
    """Check if a token is a valid hex byte or wildcard."""
    return tok == '??' or re.fullmatch(r'[0-9A-Fa-f]{2}', tok) is not None

def parse_signature_line(line):
    """Parse a signature line, accepting hex, ?? and * wildcards."""
    if '=' not in line:
        return None
    name, raw = line.strip().split('=', 1)

# Accept only allowed characters (0-9, A-F, ?, *)
    raw = raw.strip().upper().replace(' ', '')
    if not re.fullmatch(r'[0-9A-F\?\*]+', raw):
        return None

# Replace wildcards with a neutral byte (00) to allow Aho–Corasick build
    cleaned = raw.replace('??', '00').replace('*', '')
    if len(cleaned) % 2 != 0:
        return None  # Not a valid even-length hex string
    return cleaned

def e(sf):
    """Load and validate .db signature file."""
    p = []
    skipped = 0
    try:
        if os.path.getsize(sf) == 0:
            raise ValueError("Empty signature file.")

with open(sf, 'r', encoding='utf-8') as u:
            for v in u:
                if '=' in v:
                    parsed = parse_signature_line(v)
                    if parsed:
                        p.append(parsed)
                    else:
                        skipped += 1

if not p:
            raise ValueError("No valid signatures loaded.")

r = b(p)
        d(r)
        msg = f"Loaded {len(p)} valid signatures"
        if skipped:
            msg += f", skipped {skipped} invalid lines."
        m.showinfo("Signature File Loaded", msg)
        return r, len(p)
    except Exception as ex:
        m.showerror("Error", f"Failed to load signature file:\n{ex}")
        return None, 0

# =========================
# File scanning
# =========================
def h(fp, r, w=1024):
    """Scan a file using the constructed automaton."""
    try:
        with open(fp, 'rb') as u:
            if os.path.getsize(fp) < w:
                u.seek(0)
                v = u.read()
            else:
                v = u.read(w)
                u.seek(-w, os.SEEK_END)
                v += u.read(w)
            y = v.hex().upper()
            z = a(y, r)
            if z:
                f_, g_ = z[0]
                pos = f_ / (2 * len(v))
                return True, f"\nFile: {fp}\nMalicious! ^\nSignature: {g_}\nLocation:", pos
            return False, f"\nFile: {fp}\nClean file!\nLocation:", None
    except Exception as s:
        return False, f"\nFile: {fp}\nStatus: Error - {s}\n", None

# =========================
# GUI logic
# =========================
def j(pos, w=40):
    if pos is None:
        return "-" * w
    q = int(w * pos)
    return "-" * q + "+" + "-" * (w - q - 1)

def l():
    A = None
    B = 0

C = t.Tk()
    C.title('Hex Signature Scanner (Gagniuc - Scut Antivirus)')

def L():
        nonlocal A, B
        sf = f.askopenfilename(
            title="Select Signature File",
            filetypes=(("Database files", "*.db"), ("All files", "*.*"))
        )
        if sf:
            A, B = e(sf)
            if A:
                M.config(state=t.NORMAL)
                D.config(text=f"Total Signatures: {B}")

def Q():
        nonlocal A
        if not A:
            m.showinfo("Information", "Load signature file first.")
            return

x = {y.strip() for y in G.get().split(',')}
        if not x:
            m.showinfo("Information", "Specify file extensions to scan.")
            return

y = f.askdirectory()
        if y:
            I.delete(1.0, t.END)
            F = []
            for R, _, S in os.walk(y):
                F.extend(
                    os.path.join(R, u)
                    for u in S
                    if any(u.lower().endswith(z.lower()) for z in x)
                )
            H['maximum'] = len(F)
            ic = 0
            cc = 0
            start = time.time()
            for fp in F:
                inf, res, pos = h(fp, A)
                gp = j(pos)
                I.insert(t.END, f"{res} [{gp}]\n")
                I.update_idletasks()
                H['value'] += 1
                H.update_idletasks()
                if inf:
                    ic += 1
                else:
                    cc += 1
            end = time.time()
            elapsed = end - start
            J.config(
                text=f"Scan Summary: {ic} Infected, {cc} Clean. Time Elapsed: {elapsed:.2f} sec"
            )

K = t.Button(C, text="Load Signature", command=L)
    K.pack(pady=10)

D = t.Label(C, text="Total Signatures: 0")
    D.pack(pady=10)

G = t.Entry(C)
    G.pack(pady=10)
    G.insert(0, ".exe,.dll,.docx")

M = t.Button(C,
                 text="Browse Folder and Scan",
                 command=Q,
                 state=t.DISABLED)
    M.pack(pady=10)

H = k.Progressbar(C,
                      orient="horizontal",
                      length=300,
                      mode="determinate")
    H.pack(pady=10)

J = t.Label(C, text="Scan summary: Not started")
    J.pack(pady=10)

I = s.ScrolledText(C,
                       wrap=t.WORD,
                       width=80,
                       height=20)
    I.pack(pady=10, padx=10)

C.mainloop()

if __name__ == "__main__":
    l()

# References
# Gagniuc, P.A.; Păvăloiu, I.B.; Dascălu, M.I. The Aho-Corasick Paradigm in Modern Antivirus 
# Engines:A Cornerstone of Signature-Based Malware Detection. Algorithms 2025, 18, 742.

```
***
<div align="center">
    <img src="https://github.com/Gagniuc/Malware-Scanner/blob/main/img/screenshot.png">
</div>

***
> **Note:** The repositories below showcase a few demo algorithmic implementations provided from the total of 127 algorithms presented in 
> *Antivirus Engines: From Methods to Innovations, Design, and Applications* (Elsevier Syngress, 2024). You may find these standalone tools insightful:
> - [Ex. (17) - The Hash table](https://github.com/Gagniuc/Hash-table)
> - [Ex. (19) - Aho-Corasick algorithm](https://github.com/Gagniuc/Aho-Corasick-algorithm)
> - [Ex. (20) - The Bloom filter algorithm](https://github.com/Gagniuc/The-Bloom-filter)
> - [Ex. (42) - Hexadecimal Signature Extractor](https://github.com/Gagniuc/Hexadecimal-Signature-Extractor-for-Aho-Corasick)
> - [Ex. (49) - Optimized HEX Signature Scanner](https://github.com/Gagniuc/Aho-Corasick-Malware-Scanner)
> - [Ex. (52) - Aho-Corasick Native Malware Scanner](https://github.com/Gagniuc/Aho-Corasick-Native-Malware-Scanner)
***

## References
- <i>Gagniuc, P.A.; Păvăloiu, I.B.; Dascălu, M.I. The Aho-Corasick Paradigm in Modern Antivirus Engines: A Cornerstone of Signature-Based Malware Detection. Algorithms 2025, 18, 742.</i>
- <i>Paul A. Gagniuc. Antivirus Engines: From Methods to Innovations, Design, and Applications. Cambridge, MA: Elsevier Syngress, 2024. pp. 1-656.</i>

***

Malware-Scanner

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